Method and apparatus for recording and reproducing information on and from optical disc

ABSTRACT

An apparatus for recording and reproducing an information signal on and from an optical disc includes a memory. The information signal is written into the memory. The information signal is read out from the memory. An optical head generates a laser beam in response to the readout information signal, and applies the laser beam to the optical disc to record the readout information signal on the optical disc. A test signal is recorded on a position of the optical disc near a recording position thereof via the optical head during the writing of the information signal into the memory. The test signal is reproduced from the optical disc. The reproduced test signal is evaluated to generate an evaluation result. An intensity of the laser beam is optimized in response to the evaluation result.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an apparatus for recording and reproducinginformation on and from an optical disc. In addition, this inventionrelates to a method of recording and reproducing information on and froman optical disc. Furthermore, this invention relates to an optical disc.

2. Description of the Related Art

Optical discs contain an MD (Mini Disc). MD players include shock-proofmemories having a capacity of 4 MB which corresponds to a playback timeof about 10 seconds. During the playback mode of operation of the MDplayer, a pickup sequentially accesses sectors on an MD and reproducesdata therefrom. In the MD player, the reproduced data are temporarilystored in the shock-proof memory and are read out therefrom so that thecontents of the data are played back. When the pickup jumps from asector to a next sector, the pickup does not reproduce any data from theMD. Thus, during the playback mode of operation of the MD player, thereproduction of data from the MD by the pickup is sometimes interruptedfor a short time. The shock-proof memory absorbs such an interruption ofthe reproduction of data from the MD, thereby providing continuousplayback of the contents of the data. Specifically, data remain read outfrom the shock-proof memory and playback of the contents of the datacontinues even for a time during which the pickup jumps from a sector toa next sector while kicking across recording tracks on the MD andwaiting for disc rotation to meet the next sector.

During the recording mode of operation of the MD player, a pickupsequentially accesses sectors on the MD and records data thereon. In theMD player, compressed data to be recorded are temporarily stored in theshock-proof memory. The compressed data are intermittently read out fromthe memory before being fed to the pickup and being recorded on the MDthereby. Thus, during the recording mode of operation of the MD player,the feed of data to the pickup is intermittently executed. The absenceof data feed to the pickup is synchronized with jump of the pickup froma sector to a next sector. Accordingly, during the absence of data feed,the pickup jumps from a sector to a next sector while kicking acrossrecording tracks on the MD and waiting for disc rotation to meet thenext sector.

Optical discs contain a DVD (Digital Video Disc or Digital VersatileDisc). DVD players include shock-proof memories similar in function tothose in the MD players. Typical shock-proof memories in the DVD playershave a capacity of 16 MB which corresponds to a playback time of about 2seconds. Advanced shock-proof memories in the DVD players have acapacity of more than 16 MB which corresponds to a playback time oflonger than 2 seconds.

Optical discs are of a read only type (a playback only type), arecordable type (a write once type), and a rewritable type. A CD(Compact Disc), a VCD (Video CD), and a DVD are optical discs of theread only type. A CD-R and a DVD-R are optical discs of the recordabletype. A CD-RW, a DVD-RAM, and a DVD-RW are optical discs of therewritable type.

Optical discs of the rewritable type have thin recording films which arereversibly changed between two or more different states in accordancewith conditions of laser beams applied thereto.

Rewritable optical discs include magneto-optical discs and phase changediscs.

In the case of a phase change optical disc, while a recording film isscanned by a laser beam, the recording film is reversibly changedbetween an amorphous state and a crystalline state by changingconditions of the laser beam in response to a signal to be recorded.Thus, the signal is recorded on the recording film as a pattern ofamorphous portions and crystalline portions of the recording film. Thesignal is reproduced from the phase change optical disc as follows. Thesurface of an amorphous portion of the disc and the surface of acrystalline portion thereof are different in reflectivity with respectto a laser beam. While the phase change optical disc is scanned by alaser beam, a change in reflectivity of the disc surface with respect tothe laser beam is optically detected so that the signal is reproducedfrom the disc.

The phase change optical disc is similar to a read only optical disc anda recordable optical disc in the point that signal reproduction isimplemented by detecting a change in the disc surface reflectivity withrespect to a laser beam. Signal overwriting on the phase change opticaldisc can be performed by use of only one laser beam when the laser poweris modulated between an erasing level Pe and a recording level Pw.Therefore, the structure of a drive device for the phase change opticaldisc can be simple.

It is conceivable to use a PWM (pulse width modulation) system to recorda signal on a rewritable optical disc at a high density. According tothe PWM system, the positions of the front and rear edges of everyrecording mark on the disc correspond to “1” in a digital signal.

In the PWM system, the width of every recording mark representsinformation. Thus, a desirable shape of the recording mark is free fromdistortion. Specifically, it is desirable that the shapes of the front-and rear halves of the recording mark are symmetrical with each other.During the PWM-based recording of a signal on the disc, the disc isexposed to a laser beam while being rotated and moved relative thereto.In addition, the intensity of the laser beam is changed between strongand weak levels in response to the signal to be recorded. Recordingmarks are formed on portions of the disc which are exposed to thestronger laser beam. Regarding every recording mark, the heataccumulation effect causes the stronger-beam-application ending point onthe disc to be higher in temperature than the stronger-beam-applicationstarting point on the disc. As a result, the rear end of the recordingmark is wider than the front end thereof. Thus, the shape of therecording mark is distorted.

Japanese published unexamined patent application 3-185628 discloses amethod of reducing distortion in the shape of a recording mark. Themethod in Japanese application 3-185628 is an overwriting method inwhich one recording mark is formed by the application of a train ofshort pulses (narrow pulses) of a laser beam to a disc.

Japanese published unexamined patent application 6-12674 discloses amethod of correcting the waveform of a train of electric pulses fed to alaser source. According to the method in Japanese application 6-12674,an input signal repetitively changes between a high level state and alow level state. The input signal being continuously in the high levelstate corresponds to one recording mark. The input signal beingcontinuously in the high level state is converted into a train ofelectric short pulses (electric narrow pulses). The first pulse in thetrain is wider than the second and later pulses therein. The number ofthe pulses in the train is determined by a desired length of therecording mark. The electric pulse train is fed to the laser source. Theelectric pulse train is converted by the laser source into acorresponding train of short pulses (narrow pulses) of a laser beam. Thelaser beam pulse train is applied to a disc. One recording mark isformed on the disc in response to the laser beam pulse train. Since thefirst pulse in the train is relatively wide, the temperature of thebeam-train-application starting point on the disc quickly rises. On theother hand, since the second and later pulses in the train arerelatively narrow, the temperature of the beam-train-application endingpoint on the disc is prevented from excessively rising. Therefore, it ispossible to compensate for the heat accumulation effect which wouldcause distortion of the recording mark.

The shape-distortion reducing technique in Japanese application 6-12674is less effective as the linear velocity related to the scanning of adisc increases. In the method of Japanese application 6-12674, a trainof short pulses (narrow pulses) of a laser beam is applied to therecording film of a disc to form a recording mark thereon. The pulsativelaser beam results in decreased energy applied to the recording film ofthe disc. Accordingly, a required instantaneous power of the laser beamis relatively high. In addition, a required instantaneous power of thelaser beam rises as the linear velocity related to the scanning of thedisc increases. A high-power laser source is expensive.

In the method of Japanese application 6-12674, the input signal beingcontinuously in the high level state is converted into a train ofelectric short pulses. It is necessary to use a clock signal in theconversion of the high-level input signal into the electric pulse train.The period of the clock signal is equal to the period of the inputsignal which is divided by a given integer. As the frequency of theinput signal rises, the required frequency of the clock signalincreases. An excessively high frequency of the clock signal causesdifficulty in circuit designing. Modulation of the laser power at ahigher frequency causes greater distortion in the waveform of the laserbeam.

In a CAV (constant angular velocity) disc drive system, a disc isrotated at a constant angular speed. In this case, the linear velocityrelated to the scanning of an outer portion of the disc is higher thanthat of an inner portion of the disc. According to a proposed method,the length of a recording mark on an inner portion of a disc and thelength of that on an outer portion of the disc are set the same toincrease the recording density. In the proposed method, the recordingfrequency at a position on the disc increases as the position is closerto the outer edge of the disc.

In a CLV (constant linear velocity) disc drive system, a disc is rotatedat a constant linear speed. A conceivable CLV recording apparatus isable to record signals on discs of different types. The conceivable CLVrecording apparatus is required to change the linear velocity and therecording frequency depending on the disc type.

Optimal recording conditions of a disc having a high recording densityvary from disc to disc. In addition, the optimal recording conditionsdepend on the number of times of signal recording on the disc, theambient temperature, and other factors. According to a conceivablemethod of detecting optimal recording conditions of a disc, signalrecording on the disc is interrupted, and a recording head is moved to atest area of the disc. Then, a test signal is recorded on the test area,and the test signal is reproduced therefrom. The quality of thereproduced test signal is measured. Optimal recording conditions of thedisc are detected on the basis of the measurement results. After theoptimal recording conditions are detected, the recording of a maininformation signal on the disc is started. The recording of the maininformation signal is implemented under the optimal recordingconditions. In the conceivable method, the detection of optimalrecording conditions takes a long time. Thus, there is a long wait untilthe recording of the main information signal on the disc is started.

The power of a laser beam depends on the ambient temperature and theaging of a laser source. To maintain accurate signal recording on adisc, it is necessary to compensate for such a variation in the power ofthe laser beam. In a conceivable method, signal recording on the disc isinterrupted, and the power of a laser beam is measured. Optimal driveconditions of a laser source are decided on the basis of the measurementresults. In the conceivable method, the decision as to optimal driveconditions of the laser source takes a long time.

A prior-art method of detecting optimal recording conditions of a CD-Rhas a step of measuring the asymmetry of a reproduced signal. A DVD-R, aDVD-RW, other organic-dye recordable optical discs, other phase changerewritable optical discs, and other recordable and rewritable opticaldiscs having high recording densities are made from various selectionsof materials in various fabrication methods. Therefore, if the prior-artmethod is applied to such a high-recording-density disc, the results ofthe detection of optimal recording conditions are unreliable.

A phase change optical disc has the following problem. As a same signalis repetitively recorded on a same position on the disc at a sametiming, the jitter-related quality of a signal reproduced therefromdeteriorates.

SUMMARY OF THE INVENTION

It is a first object of this invention to provide an improved apparatusfor recording and reproducing information on and from an optical disc.

It is a second object of this invention to provide an improved method ofrecording and reproducing information on and from an optical disc.

It is a third object of this invention to provide an improved opticaldisc.

A first aspect of this invention provides an apparatus for recording andreproducing an information signal on and from an optical disc. Theapparatus comprises a memory; means for writing the information signalinto the memory; means for reading out the information signal from thememory; an optical head for generating a laser beam in response to thereadout information signal, and applying the laser beam to the opticaldisc to record the readout information signal on the optical disc; meansfor recording a test signal on a position of the optical disc near arecording position thereof via the optical head during the writing ofthe information signal into the memory; means for reproducing the testsignal from the optical disc; means for evaluating the reproduced testsignal to generate an evaluation result; and means for optimizing anintensity of the laser beam in response to the evaluation result.

A second aspect of this invention provides an apparatus for recordingand reproducing an information signal on and from an optical disc. Theapparatus comprises a memory; means for writing the information signalinto the memory; means for reading out the information signal from thememory; an optical head for generating a laser beam in response to thereadout information signal, and applying the laser beam to the opticaldisc to record the readout information signal on the optical disc; meansfor changing a power of the laser beam among a plurality of differentlevels; means for measuring the laser beam to generate measurementresult values during the change of the power of the laser beam among theplurality of the different levels; and means for optimizing an intensityof the laser beam in response to the measurement result values.

A third aspect of this invention is based on the first aspect thereof,and provides an apparatus wherein the test signal comprises a testpattern signal, and the recording means comprises means for recordingthe test pattern signal on the optical disc via the optical head whilechanging an intensity of the laser beam among a plurality of differentlevels for a testing purpose, and wherein the reproducing meanscomprises means for reproducing the test pattern signal from the opticaldisc, and the evaluating means comprises means for evaluating at leastone of asymmetry and jitter of the reproduced test pattern signal togenerate the evaluation result.

A fourth aspect of this invention is based on the second aspect thereof,and provides an apparatus further comprising means for repetitivelymeasuring the laser beam to repetitively generate a measurement resultvalue, means for calculating a difference between a current measurementresult value and an immediately preceding measurement result value, andmeans for enabling the optimizing means to optimize the intensity of thelaser beam when the calculated difference is equal to or greater than apredetermined value.

A fifth aspect of this invention is based on the first aspect thereof,and provides an apparatus further comprising means for repetitivelymeasuring a temperature to repetitively generate a measured temperaturevalue, means for calculating a difference between a current measuredtemperature value and an immediately preceding measured temperaturevalue, and means for enabling the optimizing means to optimize theintensity of the laser beam when the calculated difference is equal toor greater than a predetermined value.

A sixth aspect of this invention is based on the first aspect thereof,and provides an apparatus further comprising means for measuring a lapseof time since a moment of the last optimization of the intensity of thelaser beam, and for deciding whether or not the measured lapse of timeexceeds a predetermined time to generate a decision result, and meansfor optimizing the intensity of the laser beam in response to thedecision result.

A seventh aspect of this invention is based on the first aspect thereof,and provides an apparatus further comprising means for measuring adistance between a current recording position and a next recordingposition on the optical disc, and deciding whether or not the measureddistance exceeds a predetermined distance to generate a decision result,and means for optimizing the intensity of the laser beam in response tothe decision result.

An eighth aspect of this invention provides a method of recording andreproducing an information signal on and from an optical disc. Themethod comprises the steps of writing an information signal into amemory; reading out the information signal from the memory; generating alaser beam in response to the readout information signal, and applyingthe laser-beam to the optical disc to record the readout informationsignal on the optical disc; recording a test signal on a position of theoptical disc near a recording position thereof via the optical headduring the writing of the information signal into the memory;reproducing the test signal from the optical disc; evaluating thereproduced test signal to generate an evaluation result; and optimizingan intensity of the laser beam in response to the evaluation result.

A ninth aspect of this invention provides an optical disc having an areastoring information of an intensity of a laser beam which has beenoptimized by the apparatus of the first aspect of this invention.

A tenth aspect of this invention provides n apparatus for recording andreproducing an information signal on and from an optical disc. Theapparatus comprises a memory; means for writing the information signalinto the memory; means for reading out the information signal from thememory; an optical head for generating a laser beam in response to thereadout information signal, and applying the laser beam to the opticaldisc to record the readout information signal on the optical disc; meansfor recording a test signal on a position of the optical disc near arecording position thereof via the optical head during the writing ofthe information signal into the memory; means for reproducing the testsignal from the optical disc; first optimizing means for measuringasymmetry of the reproduced test signal, and optimizing an intensity ofthe laser beam in response to the measured asymmetry; second optimizingmeans for measuring jitter of the reproduced test signal, and optimizingthe intensity of the laser beam in response to the measured jitter;third optimizing means for measuring the laser beam to generate ameasurement result, and optimizing the intensity of the laser beam inresponse to the measurement result; means for detecting a type of theoptical disc; and means for selecting at least one of the first, second,and third optimizing means in response to the detected type, andenabling the selected one of the first, second, and third optimizingmeans.

An eleventh aspect of this invention is based on the tenth aspectthereof, and provides an apparatus wherein the type detecting meanscomprises means for deciding whether the type of the optical disc is anorganic-dye type or a phase change type to generate a type decisionresult, and the selecting means comprises means for selecting at leastone of the first, second, and third optimizing means in response to thetype decision result, and enabling the selected one of the first,second, and third optimizing means.

A twelfth aspect of this invention is based on the tenth aspect thereof,and provides an apparatus wherein the type detecting means comprisesmeans for reproducing disc information from the optical disc, and meansfor deriving a disc maker from the reproduced disc information, andwherein the selecting means comprises means for selecting at least oneof the first, second, and third optimizing means in response to the discmaker, and enabling the selected one of the first, second, and thirdoptimizing means.

A thirteenth aspect of this invention is based on the tenth aspectthereof, and provides an apparatus wherein the type detecting meanscomprises means for reproducing disc information from the optical disc,and means for deriving a disc article number from the reproduced discinformation, and wherein the selecting means comprises means forselecting at least one of the first, second, and third optimizing meansin response to the disc article number, and enabling the selected one ofthe first, second, and third optimizing means.

A fourteenth aspect of this invention is based on the tenth aspectthereof, and provides an apparatus wherein the type detecting meanscomprises means for reproducing disc information from the optical disc,and means for deriving a disc production lot number from the reproduceddisc information, and wherein the selecting means comprises means forselecting at least one of the first, second, and third optimizing meansin response to the disc production lot number, and enabling the selectedone of the first, second, and third optimizing means.

A fifteenth aspect of this invention provides an apparatus for recordingand reproducing an information signal on and from an optical disc. Theapparatus comprises a memory; means for writing the information signalinto the memory; means for reading out the information signal from thememory; an optical head for generating a laser beam in response to thereadout information signal, and applying the laser beam to the opticaldisc to record the readout information signal on the optical disc; meansfor repetitively recording a test signal on a place on the optical discvia the optical head, the place being near a recording position of theoptical disc which is subjected to signal recording next; means forreproducing the test signal from the optical disc; means for evaluatingthe reproduced test signal to generate an evaluation result; means foroptimizing an intensity of the laser beam in response to the evaluationresult; and means for changing the test signal on arecording-by-recording basis.

A sixteenth aspect of this invention is based on the fifteenth aspectthereof, and provides an apparatus wherein the changing means comprisesmeans for generating a random signal providing a random timing, andmeans for shifting the test signal in response to the random timing tochange the test signal on the recording-by-recording basis.

A seventeenth aspect of this invention is based on the fifteenth aspectthereof, and provides an apparatus wherein the changing means comprisesmeans for time-positionally exchanging signal segments of the testsignal to change the test signal on the recording-by-recording basis.

An eighteenth aspect of this invention provides an apparatus forrecording and reproducing an information signal on and from an opticaldisc. The apparatus comprises means for generating a laser beam inresponse to a first time segment of the information signal, and applyingthe laser beam to a first place on the optical disc to record the firsttime segment of the information signal on the first place on the opticaldisc; means for generating a laser beam in response to a test signal,and applying the laser beam to a second place on the optical disc torecord the test signal on the second place on the optical disc whilechanging the laser beam among a plurality of conditions different fromeach other, the second place immediately following the first place;means for reproducing the test signal from the optical disc; means forevaluating the reproduced test signal to generate evaluation resultscorresponding to the respective different conditions of the laser beam;means for deciding a best of the evaluation results; and means forgenerating a laser beam in one of the different conditions whichcorresponds to the best evaluation result and in response to a secondtime segment of the information signal, and applying the laser beam tothe second place on the optical disc to write the second time segment ofthe information signal over the test signal on the second place on theoptical disc, the second time segment immediately following the firsttime segment.

A nineteenth aspect of this invention is based on the eighteenth aspectthereof, and provides an apparatus wherein the different conditions ofthe laser beam comprise different conditions of pulses in pulse trainsof the laser beam.

A twentieth aspect of this invention provides an apparatus for recordingand reproducing an information signal on and from an optical disc. Theapparatus comprises a memory; means for writing the information signalinto the memory; means for reading out the information signal from thememory; an optical head for generating a laser beam in response to thereadout information signal, and applying the laser beam to the opticaldisc to record the readout information signal on the optical disc; meansfor recording a test signal on the optical disc via the optical headwhile changing the laser beam among a plurality of conditions differentfrom each other for a testing purpose during the writing of theinformation signal into the memory; means for reproducing the testsignal from the optical disc; means for evaluating the reproduced testsignal to generate evaluation results corresponding to the respectivedifferent conditions of the laser beam; means for deciding a best of theevaluation results; and means for controlling the laser beam into one ofthe different conditions which corresponds to the best evaluationresult.

A twenty-first aspect of this invention is based on the twentieth aspectthereof, and provides an apparatus wherein the different conditions ofthe laser beam comprise different conditions of pulses in pulse trainsof the laser beam.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a time-domain diagram of a waveform of an input signal, andrecording waveforms of a laser beam.

FIG. 2 is a sectional view of a portion of an optical disc.

FIG. 3 is a time-domain diagram of a waveform of an input signal, andrecording waveforms of a laser beam.

FIG. 4 is a diagram of the relation between a disc-scanning linearvelocity and a phase margin.

FIG. 5 is a diagram of the relation among the disc-scanning linearvelocity, the phase margin, and a temperature.

FIG. 6 is a diagram of the relation between the disc-scanning linearvelocity and a recording power.

FIG. 7 is a diagram of a recording waveform of a laser beam.

FIG. 8 is a diagram of a recording waveform of a laser beam.

FIG. 9 is a block diagram of an information-signal recording andreproducing apparatus according to a first embodiment of this invention.

FIG. 10 is a diagrammatic plan view of an optical disc.

FIG. 11 is a block diagram of an amplifier unit in FIG. 9.

FIG. 12 is a diagram of addresses on an optical disc, and data recordedon the disc.

FIG. 13 is a time-domain diagram of the degree of the occupancy of amemory in FIG. 9.

FIG. 14 is a flowchart of a segment of a program for a system controllerin FIG. 9.

FIG. 15 is a flowchart of a block in FIG. 14.

FIG. 16 is a block diagram of an asymmetry detection circuit in FIG. 11.

FIG. 17 is a flowchart of a block in a program segment in a secondembodiment of this invention.

FIG. 18 is a flowchart of a block in a program segment in a thirdembodiment of this invention.

FIG. 19 is a flowchart of a block in a program segment in a fourthembodiment of this invention.

FIG. 20 is a flowchart of a block in a program segment in a fifthembodiment of this invention.

FIG. 21 is a flowchart of a block in a program segment in a sixthembodiment of this invention.

FIG. 22 is a flowchart of a block in a program segment in a seventhembodiment of this invention.

FIG. 23 is a flowchart of a block in a program segment in a fifteenthembodiment of this invention.

FIG. 24 is a diagram of a recording waveform of a laser beam.

FIG. 25 is a diagram of a recording waveform of a laser beam.

FIG. 26 is a flowchart of a program segment in a twenty-seventhembodiment of this invention.

FIG. 27 is a flowchart of a program segment in a twenty-ninth embodimentof this invention.

FIG. 28 is a time-domain diagram of a wobble signal, a recording clocksignal, an LPP signal, and a timing signal.

FIG. 29 is a block diagram of a waveform correction circuit in FIG. 11.

DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

A first embodiment of this invention is designed to correct a recordinglaser beam into an optimal waveform in accordance with the type of anoptical disc and a variation in the linear velocity related to thescanning of the disc.

As shown in FIG. 1, an input signal (for example, an 8-16modulation-resultant signal) repetitively changes between a high levelstate and a low level state. In the case where the linear velocityrelated to the scanning of the disc is lower than a preset velocity, alaser beam is modulated into a recording waveform WAO having trains ofshort pulses (narrow pulses). The power of the laser beam changesbetween an erasing level Pe and a recording level Pw. Each laser-beampulse train in the recording waveform WAO corresponds to the inputsignal being continuously in the high level state. The first pulse inthe train is wider than the second and later pulses therein. The numberof the pulses in the train increases as the time interval for which theinput signal is continuously in the high level state increases.

In the case where the linear velocity related to the scanning of thedisc is equal to or higher than the preset velocity the laser beam ismodulated into a recording waveform WBO having wide pulses as shown inFIG. 1. The power of the laser beam changes between an erasing level Peand a recording level Pw. Each laser-beam pulse in the recordingwaveform WBO corresponds to the input signal being continuously in thehigh level state. The duration of the laser-beam pulse is slightlyshorter than the corresponding time interval for which the input signalis continuously in the high level state.

Experiments were performed to determine the relation between the linearvelocity related to the scanning of a phase change optical disc and thewaveform distortion of a signal reproduced from the disc. During theexperiments, signal recording on and signal reproduction from the discwere implemented while the linear velocity and the recording waveformwere changed.

As shown in FIG. 2, the phase change optical disc used in theexperiments included a substrate 1 made of polycarbonate. The disc had adiameter of 120 mm. The disc was formed with a signal recording track. Adielectric film 3, a recording film 2, a dielectric film 4, and areflecting layer 5 were sequentially laminated on the substrate 1 inthat order. The recording film 2 was made of GeSbTe. The recording film2 had a thickness of 20 nm. The dielectric films 3 and 4 were made ofZnS. The dielectric film 3 had a thickness of 150 nm. The dielectricfilm 4 had a thickness of 15 nm. The reflecting film 5 was made of Au.The reflecting film 5 had a thickness of 50 nm.

After the whole surface of the recording film 2 of the disc wascrystallized (that is, after a signal was completely erased from thewhole surface of the recording film 2 of the disc), the disc was scannedby a laser beam responsive to an input signal. Specifically, while thedisc was rotated, the laser beam having a recording power level wasintermittently applied to the surface of the recording film 2 inresponse to the input signal. Portions of the surface of the recordingfilm 2 which were exposed to the recording-power-level laser beamchanged to an amorphous state. Thus, the input signal was recorded onthe recording film 2 as recording marks formed by the respectiveamorphous portions of the surface of the recording film 2. The linearvelocity related to the scanning of the disc was changed among 1.5 m/s,3 m/s, 6 m/s, and 9 m/s. The input signal was an 8-16modulation-resultant signal. The laser beam was emitted from asemiconductor laser. The input signal was recorded on the disc by usinga laser-beam recording waveform WA based on the recording waveform WAO(see FIG. 1). In addition, the input signal was recorded on the disc byusing a laser-beam recording waveform WB corresponding to the recordingwaveform WBO (see FIG. 1).

As shown in FIG. 3, the 8-16 modulation-resultant signal (the inputsignal) repetitively changed between a high level state and a low levelstate. A clock signal (a bit clock signal) related to the 8-16modulation-resultant signal had a period T. The period T is alsoindicated as T. As shown in FIG. 3, the laser-beam recording waveform WAwas generated in response to the 8-16 modulation-resultant signal (theinput signal). According to the laser-beam recording waveform WA, thepower (or the intensity) of the laser beam changed between an erasinglevel Pb and a recording level Pp. It should be noted that the erasinglevel Pb and the recording level Pp may be variable. The laser-beamrecording waveform WA had trains of short pulses (narrow pulses). Eachlaser-beam pulse train in the recording waveform WA corresponded to the8-16 modulation-resultant signal being continuously in the high levelstate. The moment of the occurrence of the leading edge of the firstpulse in the train follows the moment of the occurrence of the risingedge in the 8-16 modulation-resultant signal by a time interval Ta setto T. The first pulse in the train had a width or duration Tb set to1.5T. The second and later pulses in the train had a width or durationTd set to 0.5T. In the train, the pulses were spaced at intervals Tc setto 0.5T. It should be noted that the time intervals Ta, Tb, Tc, and Tdmay be variable. A clock signal used to generate the laser-beamrecording waveform WA had a frequency equal to twice the frequency ofthe clock signal related to the 8-16 modulation-resultant signal.

As shown in FIG. 3, the laser-beam recording waveform WB was generatedin response to the 8-16 modulation-resultant signal (the input signal).According to the laser-beam recording waveform WB, the power (or theintensity) of the laser beam changed between an erasing level Pb and arecording level Pp. The laser-beam recording waveform WB had widepulses. Each laser-beam pulse in the recording waveform WB correspondedto the 8-16 modulation-resultant signal being continuously in the highlevel state. The duration of the laser-beam pulse is shorter than thecorresponding time interval for which the input signal is continuouslyin the high level state by a value set to T. The moment of theoccurrence of the leading edge of the laser-beam pulse follows themoment of the occurrence of the rising edge in the 8-16modulation-resultant signal by a time interval set to T.

The frequency of the clock signal related to the 8-16modulation-resultant signal was varied in response to the disc-scanninglinear velocity so that the lengths of recording marks on the discremained constant independent of the disc-scanning linear velocity.Specifically, the clock frequency was 4.3 MHz when the linear velocitywas 1.5 m/s. The clock frequency was 8.6 MHz when the linear velocitywas 3 m/s. The clock frequency was 17.2 MHz when the linear velocity was6 m/s. The clock frequency was 25.8 MHz when the linear velocity was 9m/s.

After the signal was recorded on the disc, the signal was reproducedtherefrom. The waveform distortion of the reproduced signal wasquantitatively evaluated. Specifically, the reproduced signal wasconverted into a binary signal (a two-level signal). The binary signalwas inputted into a time interval analyzer so that the jitter amount ofthe binary signal was detected as a phase margin. The errors of thepositions of the front and rear edges of recording marks decreased andhence the distortions of the recording marks decreased as the phasemargin increased.

During the experiments, the phase margin was measured for each ofoptical discs of several types. FIG. 4 shows the experimentally obtainedrelation between the variation in the phase margin and the linearvelocity related to the scanning of the discs. The recording waveform WAwas used when the linear velocity was 1.5 m/s, 3.0 m/s, and 6.0 m/s. Therecording waveform WB was used when the linear velocity was 9.0 m/s.With reference to FIG. 4, the phase margin increased as the linearvelocity increased. As shown in FIG. 5, the relation between the phasemargin and the disc-scanning linear velocity depended on the ambienttemperature of the disc. Specifically, the phase margin increased as theambient temperature of the disc rose. As shown in FIG. 6, the recordingpower level Pp of the laser beam on the disc and having the waveform WAwas increased in accordance with an increase in the disc-scanning linearvelocity. The erasing power level Pb of the laser beam on the discremained constant regardless of the type of the recording waveform andindependent of the disc-scanning linear velocity.

As is clear from FIG. 4, the recording waveform WA is good in that thephase margin increases as the disc-scanning velocity increases. In thecase of the recording waveform WA, the phase margin varies from disc todisc. It is revealed in FIG. 5 that the phase margin depends on theambient disc temperature. The cause of the dependency of the phasemargin on the ambient disc temperature is as follows. Signal overwritingon the disc is governed by the temperature to which the recording filmof the disc is heated. The temperature to which the recording film ofthe disc is heated deviates from the optimal value due to a fluctuationin the disc-scanning linear velocity, a variation in the ambient disctemperature, and a disc-by-disc variation in the disc conditions. Asshown in FIG. 6, the recording power level Pp of the laser beam is setrelatively great since the recording waveform WA applies pulsativeenergy to the recording film of the disc. Thus, a high-powersemiconductor laser is used for drive of the disc at a high linearvelocity.

FIG. 7 shows a laser-beam recording waveform WC which may replace thelaser-beam recording waveform WA (see FIG. 3). The recording waveform WCis similar to the recording waveform WA except for the following points.In the recording waveform WC of FIG. 7, during a limited time intervalimmediately preceding each pulse train, the power of a laser beam islower than an erasing level Pb. Also, during a limited time intervalimmediately following each pulse train, the power of the laser beam islower than the erasing level Pb. In the case where intervals betweenrecording marks are relatively narrow, there occurs heat interferencesuch that heat of forming a recording mark diffuses rearward into a discportion to be exposed to a recording-power laser beam next and hence anext recording mark has a greater size. The recording waveform WCreduces the effect of heat interference. Thus, the recording waveform WCis advantageous in increasing the phase margin. In the case where thelimited time interval for which the power of the laser beam is lowerthan the erasing level Pb is excessively long, the recording film of thedisc does not reach the crystallization temperature and hence therecorded signal fails to be erased. To prevent such a problem, it ispreferable that the limited time interval “τ” for which the power of thelaser beam is lower than the erasing level Pb has the following relationwith the wavelength “λ” of the laser beam and the relative speed ‘V’between the laser beam spot and the disc.τ≦λ/V  (1)As long as the relation (1) is satisfied, the recording film in a discportion assigned to a recording mark is surely heated to thecrystallization temperature by application of the recording-power laserbeam thereto and also application of the erasing-power laser beam to aprevious disc portion.

The laser-beam recording waveform WC may be modified as follows.According to a first modification of the laser-beam recording waveformWC, only during the limited time interval immediately preceding eachpulse train, the power of a laser beam is lower than the erasing levelPb. According to a second modification of the laser-beam recordingwaveform WC, only during the limited time interval immediately followingeach pulse train, the power of the laser beam is lower than the erasinglevel Pb.

In the laser-beam recording waveform WC, the low power level of thelaser beam which occurs during every limited time interval may be equalto a reproducing power level or a null power level. In this case, thestructure of the disc drive can be simple.

The laser-beam recording waveform WB (see FIG. 3) may be modified asfollows. According to a first modification of the laser-beam recordingwaveform WB, during a limited time interval immediately preceding eachpulse, the power of a laser beam is lower than the erasing level Pb.Also, during a limited time interval immediately following each pulse,the power of the laser beam is lower than the erasing level Pb.According to a second modification of the laser-beam recording waveformWB, only during the limited time interval immediately preceding eachpulse, the power of the laser beam is lower than the erasing level Pb.According to a third modification of the laser-beam recording waveformWB, only during the limited time interval immediately following eachpulse, the power of the laser beam is lower than the erasing level Pb.

FIG. 8 shows a laser-beam recording waveform WD which may replace thelaser-beam recording waveform WC (see FIG. 7) or the laser-beamrecording waveform WA (see FIG. 3). The recording waveform WD is similarto the recording waveform WC except for the following point. Accordingto the recording waveform WD of FIG. 8, in each pulse train, the powerof a laser beam changes between a recording level Pp and a reproducinglevel (or a null level). The recording waveform WD causes every positionin a recording mark to be quickly cooled after being melt. Thus, it ispossible to stably form a recording mark. In addition, the recordingwaveform WD is advantageous in increasing the phase margin.

FIG. 9 shows an information-signal recording and reproducing apparatusaccording to the first embodiment of this invention. The apparatus ofFIG. 9 operates on a rewritable optical disc such as a DVD-RW. TheDVD-RW is driven on a CLV basis. The DVD-RW has sectors extending alonga spiral recording track. One sector has 16 bytes assigned to anaddress, and 2,048 bytes assigned to data. Regarding the DVD-RW, one ECCblock having 16 sectors is a minimum unit of error correction. Also, oneECC block is a minimum unit for signal reproduction from and signalrecording on the DVD-RW.

As shown in FIG. 10, the DVD-RW is divided into an inner area EA and anouter area EB. When the inner edge of the area EA is scanned by a laserbeam, the period of rotation of the disc is equal to about 40 msec. Whenthe outer edge of the area EB is scanned by the laser beam, the periodof rotation of the disc is equal to about 80 msec.

The DVD-RW in FIG. 10 may be designed as follows. In the inner area EA,2 ECC blocks each having 16 sectors compose a general 1-unitcorresponding block (a general reproduction and recording unit). In theouter area EB, 4 ECC blocks compose a general 1-unit corresponding block(a general reproduction and recording unit).

The apparatus of FIG. 9 includes a key input unit 10, a systemcontroller 12, a signal processor 14, a servo processor 16, a driver 18,a spindle motor 20, an optical head (optical pickup) 24, an amplifierunit 26, a memory 28, an audio-video encoding and decoding unit 30, amemory 32, an input/output terminal 34, and a temperature sensor 36.

The spindle motor 20 acts to rotate a rewritable optical disc 22 such asa DVD-RW. While the spindle motor 20 rotates the optical disc 22, theoptical head 24 writes and reads information thereon and therefrom. Thespindle motor 20 is connected to the driver 18. The optical head 24 isconnected to the amplifier unit 26 and the driver 18. The amplifier unit26 is connected to the servo processor 16 and the signal processor 14.The driver 18 is connected to the servo processor 16. The signalprocessor 14 is connected to the memory 28 and the audio-video encodingand decoding unit 30. The audio-video encoding and decoding unit 30 isconnected to the memory 32 and the input/output terminal 34. The systemcontroller 12 is connected to the key input unit 10, the signalprocessor 14, the servo processor 16, the amplifier unit 26, and theaudio-video encoding and decoding unit 30. The temperature sensor 36 islocated near the optical disc 22 placed in position within theapparatus. The temperature sensor 36 detects an ambient temperature ofthe optical disc 22. The temperature sensor 36 is connected to theamplifier unit 26.

The spindle motor 20 is driven and controlled by the driver 18. Thespindle motor 20 rotates the optical disc 22. The spindle motor 20 isprovided with an FG generator and a rotational position sensor (anangular position sensor). The rotational position sensor includes, forexample, a Hall element. The FG generator outputs an FG signal (arotational speed signal). The Hall element-outputs a rotational positionsignal. The FG signal and the rotational position signal are fed back tothe driver 18.

The optical head 24 faces the optical disc 22 placed in position withinthe apparatus. A feed motor (not shown) moves the optical head 24radially with respect to the optical disc 22. The feed motor is drivenby the driver 18. The optical head 24 includes a semiconductor laser, acollimator lens, and an objective lens. The semiconductor laser acts asa source for emitting a light beam (a laser beam). The emitted laserbeam is focused into a laser spot on the optical disc 22 by thecollimator lens and the objective lens. The optical head 24 includes a2-axis actuator for driving the objective lens to implement focusing andtracking of the laser spot with respect to the optical disc 22. Thesemiconductor laser is driven by a laser drive circuit in the amplifierunit 26. In the case where an information signal such as an audio signalor an audio-video signal is recorded, the information signal issubjected to waveform correction by a waveform correction circuit in theamplifier unit 26 before being fed to the laser drive circuit. The2-axis actuator is driven by the driver 18.

The key input unit 10 includes a plurality of keys which can be operatedby a user. The key input unit 10 generates command signals in accordancewith its operation by the user. The command signals are transmitted fromthe key input unit 10 to the system controller 12. The command signalsinclude a command signal for starting a recording mode of operation ofthe apparatus, and a command signal for starting a playback mode ofoperation of the apparatus. The key input unit 10 generates control datain accordance with its operation by the user. The control data aretransmitted from the key input unit 10 to the system controller 12.

The system controller 12 includes, for example, a microcomputer or asimilar device which operates in accordance with a program stored in itsinternal ROM. The system controller 12 controls the signal processor 14,the servo processor 16, the amplifier unit 26, and the audio-videoencoding and decoding unit 30 in response to the command signals fedfrom the key input unit 10.

Control data can be fed to the system controller 12 via an inputterminal (not shown). The control data fed to the system controller 12via the input terminal, and the control data fed to the systemcontroller 12 from the key input unit 10 include a signal for adjustingthe resolution of pictures represented by contents information to berecorded, a signal for separating quickly-moving scenes such as carracing scenes represented by contents information, and a signal forgiving priority to a recording time. The system controller 12 changes anactual recording time in accordance with the control data. The change ofthe actual recording time is implemented by changing, for example, adata compression rate used by the audio-video encoding and decoding unit30. The system controller 12 enables the setting of the actual recordingtime to be selected by the user.

When the apparatus is required to start to operate in the playback mode,the key input unit 10 is actuated to generate the playback start commandsignal. The playback start command signal is transmitted from the keyinput unit 10 to the system controller 12. The system controller 12controls the servo processor 16 and the amplifier unit 26 in response tothe playback start command signal, thereby starting the playback mode ofoperation of the apparatus. The control of the servo processor 16includes steps of controlling the driver 18. Firstly, the systemcontroller 12 starts rotation of the optical disc 22 and application ofa laser spot thereon through the control of the driver 18. The opticalhead 24 is controlled by the driver 18, thereby reading out addressinformation from the optical disc 22. The readout address information istransmitted from the optical head 24 to the system controller 12 via theamplifier unit 26. The system controller 12 finds or decides a targetsector (a target track portion) to be played back by referring to theaddress information. The system controller 12 controls the optical head24 via the servo processor 16, the driver 18, and the feed motor,thereby moving the optical head 24 radially with respect to the opticaldisc 22 and hence moving the laser spot to the target sector on theoptical disc 22. When the movement of the laser spot to the targetsector is completed, the system controller 12 operates to start thereproduction of a signal from the target sector on the optical disc 22.In this way, the playback mode of operation of the apparatus is started.During the playback mode of operation of the apparatus, the targetsector is repetitively changed from one to another.

During the playback mode of operation of the apparatus, the optical head24 scans the optical disc 22 and generates a reproduced RF signalcontaining information read out therefrom. The optical head 24 outputsthe RF signal to the amplifier unit 26. The amplifier unit 26 enlargesthe RF signal from the optical head 24. The amplifier unit 26 generatesa main reproduced signal from the enlarged. RF signal. In addition, theamplifier unit 26 generates a servo error signal (tracking and focusingservo error signals) from the output signal of the optical head 24. Theamplifier unit 26 includes an equalizer for optimizing the frequencyaspect of the main reproduced signal. Also, the amplifier unit 26includes a PLL (phase locked loop) circuit for extracting a bit clocksignal from the equalized main reproduced signal, and for generating aspeed servo signal from the equalized main reproduced signal.Furthermore, the amplifier unit 26 includes a jitter generator forcomparing the time bases of the bit clock signal and the equalized mainreproduced signal, and for detecting jitter components from the resultsof the time-base comparison. A signal of the detected jitter componentsis transmitted from the amplifier unit 26 to the system controller 12.The tracking and focusing servo signals and the speed servo signal aretransmitted from the amplifier unit 26 to the servo processor 16. Theequalized main reproduced signal is transmitted from the amplifier unit26 to the signal processor 14.

The servo processor 16 receives the speed servo signal and the trackingand focusing servo signals from the amplifier unit 26. The servoprocessor 16 receives the rotation servo signals from the spindle motor20 via the driver 18. In response to these servo signals, the servoprocessor 16 implements corresponding servo control processes.

Specifically, the servo processor 16 generates a rotation control signalon the basis of the speed servo signal and the rotation servo signals.The rotation control signal is transmitted from the servo processor 16to the spindle motor 20 via the driver 18. The spindle motor 20 rotatesat a speed depending on the rotation control signal. The rotationcontrol signal is designed to rotate the optical disc 22 at a selectedconstant linear velocity or a given constant linear velocity.

In addition, the servo processor 16 generates servo control signals onthe basis of the focusing and tracking servo signals. The servo controlsignals are transmitted from the servo processor 16 to the 2-axisactuator in the optical head 22 via the driver 18. The 2-axis actuatorcontrols the laser spot on the optical disc 22 in response to the servocontrol signals, and thereby implements focusing and tracking of thelaser spot with respect to the optical disc 22.

During the playback mode of operation of the apparatus, the signalprocessor 14 receives the main reproduced signal from the amplifier unit26. The signal processor 14 is controlled by the system controller 12,thereby converting the main reproduced signal into a correspondingreproduced digital signal. The signal processor 14 detects a sync signalfrom the reproduced digital signal. The signal processor 14 decodes an8-16 modulation-resultant signal of the reproduced digital signal intoNRZ data, that is, non-return-to-zero data. The signal processor 14subjects the NRZ data to an error correction process for everycorrection block (every ECC block), thereby generating a sector addresssignal and first and second information signals. The sector addresssignal represents the address of a currently-accessed sector on theoptical disc 22. The sync signal and the sector address signal are fedfrom the signal processor 14 to the system controller 12.

During the playback mode of operation of the apparatus, the signalprocessor 14 temporarily stores the first and second information signalsin the memory 28. Thus, the signal processor 14 writes the first andsecond information signals into the memory 28, and reads the first andsecond information signals therefrom. Writing and reading the first andsecond information signals into and from the memory 28 are controlled toabsorb a time-domain change in the transfer rates of the first andsecond information signals. The memory 28 includes, for example, a D-RAMhaving a capacity of 64 Mbytes. The signal processor 14 outputs thereadout signal (the first and second information signals read out fromthe memory 28) to the audio-video encoding and decoding unit 30.

In the case where the first and second information signals fed from thememory 28 via the signal processor 14 are compressed data (for example,MPEG2 data) in which audio data and video data are multiplexed, theaudio-video encoding and decoding unit 30 separates the first and secondinformation signals into compressed audio data and compressed videodata. The audio-video encoding and decoding unit 30 expands and decodesthe compressed audio 15, data into non-compressed audio data. Inaddition, the audio-vide encoding and decoding unit 30 expands anddecodes the compressed video data into non-compressed video data. Duringthe expansively decoding process, the audio-video encoding and decodingunit 30 temporarily stores signals and data in the memory 32. The memory32 includes, for example, a D-RAM having a capacity of 64 Mbytes. Theaudio-video encoding and decoding unit 30 converts the non-compressedaudio data into a corresponding analog audio signal throughdigital-to-analog conversion. Also, the audio-video encoding anddecoding unit 30 converts the non-compressed video data into acorresponding analog video signal through digital-to-analog conversion.The audio-video encoding and decoding unit 30 applies the analog audiosignal and the analog video signal to the input/output terminal 34. Theanalog audio signal and the analog video signal are transmitted to anexternal via the input/output terminal 34.

The data rate of the expansively decoding process by the audio-videoencoding and decoding unit 30, that is, the data transfer rate (the datatransmission rate) in the expansively decoding process, is equalized toan expansion data rate which is set in accordance with the type of therelated recording mode of operation of the apparatus. Specifically, theaudio-video encoding and decoding unit 30 can implement the expansivelydecoding process at an expansion data rate which can be changed amongplural different expansion data rates. The audio-video encoding anddecoding unit 20 selects one from among the plural different expansiondata rates as a desired expansion data rate in accordance with the typeof the related recording mode of operation of the apparatus. Theaudio-video encoding and decoding unit 30 executes the expansivelyencoding process at the desired expansion data rate. Information of thetype of the recording mode of operation of the apparatus is recorded onthe optical disc 22 as control data. During an initial stage of theplayback of the optical disc 22, the control data are read out therefrombefore being transmitted to the system controller 12. The systemcontroller 12 sets the expansion data rate in the audio-video encodingand decoding unit 30 in accordance with the control data.

When the apparatus is required to start to operate in the recordingmode, the key input unit 10 is actuated to generate the recording startcommand signal. The recording start command signal is transmitted fromthe key input unit 10 to the system controller 12; The system controller12 controls the servo processor 16 and the amplifier unit 26 in responseto the recording start command signal, thereby starting the recordingmode of operation of the apparatus. The control of the servo processor16 includes steps of controlling the driver 18. Firstly, the systemcontroller 12 starts rotation of the optical disc 22 and application ofa laser spot thereon through the control of the driver 18. The opticalhead 24 is controlled by the driver 18, thereby reading out addressinformation from the optical disc 22. The readout address information istransmitted from the optical head 24 to the system controller 12 via theamplifier unit 26. The system controller 12 finds or decides a targetsector (a target track portion), on which a signal is to be recorded, byreferring to the address information. The system controller 12 controlsthe optical head 24 via the servo processor 16 and the driver 18,thereby moving the laser spot to the target sector on the optical disc22. During the recording mode of operation of the apparatus, the targetsector is repetitively changed from one to another.

During the recording mode of operation of the apparatus, an audio signaland a video signal to be recorded are fed via the input/output terminal34 to the audio-video encoding and decoding unit 30. The audio-videoencoding and decoding unit 30 converts the audio signal intocorresponding audio data through analog-to-digital conversion. Inaddition, the audio-video encoding and decoding unit 30 converts thevideo signal into corresponding video data through analog-to-digitalconversion. The audio-video encoding and decoding unit 30 compressivelyencodes the audio data and the video data into compressed audio data andcompressed video data (for example, MPEG2 audio data and MPEG2 videodata) at a rate depending on the type of the recording mode. Theaudio-video encoding and decoding unit. 30 multiplexes the compressedaudio data and the compressed video data to form multiplexed contentsdata. The audio-vide encoding and decoding unit 30 outputs themultiplexed contents data to the signal processor 14. The data rate ofthe compressively encoding process by the audio-video encoding anddecoding unit 30, that is, the data transmission rate in thecompressively encoding process, is equalized to a compression data ratewhich is selected from among plural different rates in accordance withthe type of the recording mode of operation of the apparatus. During thecompressively encoding process, the audio-video encoding and decodingunit 30 temporarily stores data in the memory 32.

During the recording mode of operation of the apparatus, the signalprocessor 14 adds error correction code signals (ECC signals or PI andPO signals) to the multiplexed contents data. The signal processor 12subjects the ECC-added data to NRZ and 8-16 modulation encodingprocesses. The signal processor 14 adds a sync signal to theencoding-resultant contents data to form sync-added contents data. Thesync signal is fed from the system controller 12. The sync-addedcontents data are temporarily stored in the memory 28. The sync-addedcontents data are read out from the memory 28 at a data ratecorresponding to a data rate of signal recording on the optical disc 22.The signal processor 14 subjects the readout contents data to givenmodulation for record. The signal processor 14 outputs themodulation-resultant signal to the amplifier unit 26. The output signalof the signal processor 14 is an 8-16 modulation-resultant signal. Theamplifier unit 26 corrects the waveform of the output signal of thesignal processor 14. The amplifier unit 26 generates a laser drivesignal in response to the waveform-correction-resultant signal. Theamplifier unit 26 outputs the laser drive signal to the optical head 24.The optical head 24 records the output signal of the amplifier unit 26on the target sector (the target track portion) on the optical disc 22.

As shown in FIG. 11, the amplifier unit 26 includes a servo error signalgeneration circuit 49, an RF amplifier 50, an equalizer 52, a PLLcircuit 54, a jitter signal generation circuit 56, a laser drive circuit58, a waveform correction circuit 60, a switch 62, a test patterngeneration circuit 64, a temperature detection circuit 66, an asymmetrydetection circuit 70, a PLL circuit 71, a wobble detection circuit 72,an address detection circuit 73, and a timing signal generation circuit74.

The servo error signal generation circuit 49 is connected to the opticalhead 24, the servo processor 16, the wobble detection circuit 72, andthe address detection circuit 73. The wobble detection circuit 72 isconnected to the PLL circuit 71. The PLL circuit 71 is connected to thetiming signal generation circuit 74 and the signal processor 14. Theaddress detection circuit 73 is connected to the timing signalgeneration circuit 74, the system controller 12, and the signalprocessor 14. The timing signal generation circuit 74 is connected tothe jitter signal generation circuit 56, the asymmetry detection circuit70, the test pattern generation circuit 64, the system controller 12,and the signal processor 14.

The RF amplifier 50 is connected to the optical head 24, the equalizer52, and the asymmetry detection circuit 70. The equalizer 52 isconnected to the PLL circuit 54. The PLL circuit 54 is connected to thejitter signal generation circuit 56 and the signal processor 14. Thejitter signal generation circuit 56 is connected to the systemcontroller 12. The asymmetry detection circuit 70 is connected to thesystem controller 12.

The switch 62 is connected to the waveform correction circuit 60, thetest pattern generation circuit 64, the system controller 12, and thesignal processor 14. The test pattern generation circuit 64 is connectedto the system controller 12. The waveform correction circuit 60 isconnected to the laser drive circuit 58 and the system controller 12.The laser drive circuit 58 is connected to the optical head 24 and thesystem controller 12. The temperature detection circuit 66 is connected-to the temperature sensor 36 and the system controller 12. Thetemperature detection circuit 66 is an interface between the temperaturesensor 36 and the system controller 12. A signal representative of theambient temperature of the optical disc 22 is transmitted from thetemperature sensor 36 to the system controller 12 via the temperaturedetection circuit 66. The temperature sensor 36 may be replaced by atemperature-responsive semiconductor such as a temperature-responsivediode provided in the amplifier unit 26. In this case, the temperaturedetection circuit 66 receives a signal generated by thetemperature-responsive semiconductor.

The amplifier unit 26 operates as follows. The servo error signalgeneration circuit 49 in the amplifier unit 26 produces a servo errorsignal from the output signal of the optical head 24. The servo errorsignal generation circuit 49 outputs the servo error signal to the servoprocessor 16. During the playback mode of operation of the apparatus,the RF amplifier 50 enlarges the output signal of the optical head 24.The RF amplifier 50 outputs the enlarged signal to the equalizer 52 andthe asymmetry detection circuit 70. The equalizer 52 optimizes thefrequency aspect of the enlarged signal. The equalizer 52 outputs theresultant signal to the PLL circuit 54. The PLL circuit 54 subjects theoutput signal of the equalizer 52 to PLL control, thereby generatingreproduced data (read data), a bit clock signal, and a speed servosignal (a signal representing the rotational speed of the optical disc22). The PLL circuit 54 outputs the reproduced data (the read data) tothe jitter signal generation circuit 56 and the signal processor 14. ThePLL circuit 54 outputs the bit clock signal to the jitter signalgeneration circuit 56. The PLL circuit 54 outputs the speed servo signalto the servo processor 16. The jitter signal generation circuit 56compares the time bases of the reproduced data and the bit clock signal,thereby detecting jitter components and generating a signal of thedetected jitter components. The jitter signal generation circuit 56outputs the signal of the jitter components to the system controller 12.The timing of the jitter detection by the jitter signal generationcircuit 56 is controlled by the timing signal generation circuit 74.

The output signal of the RF amplifier 50 contains a reproduced 8-16modulation-resultant signal during the playback mode of operation of theapparatus. The asymmetry detection circuit 70 decides, from the outputsignal of the RF amplifier 50, the position of the center of ashortest-period signal “3T” relative to the peak and bottom amplitudepositions of a longest-period signal “11T” of the reproduced 8-16modulation-resultant signal. The asymmetry detection circuit 70 informsthe system controller 12 of the decision result as a detected asymmetryvalue. The decision by the asymmetry detection circuit 70 corresponds tothe detection of an asymmetry. The timing of the asymmetry detection bythe asymmetry detection circuit 70 is controlled by the timing signalgeneration circuit 74. The wobble detection circuit 72 generates awobble signal (a frequency signal) from an output signal of the servoerror signal generation circuit 49. The wobble detection circuit 72outputs the wobble signal to the PLL circuit 71. The PLL circuit 71generates a spindle speed signal and a recording clock signal inresponse to the wobble signal The PLL circuit 71 outputs the spindlespeed signal and the recording clock signal to the timing signalgeneration circuit 74 and the system controller 12. The addressgeneration circuit 73 produces a signal of an address on the opticaldisc 22 and a recording/reproduction timing signal (a land pre-pitsignal or an LPP signal) in response to the output signal of the servoerror signal generation circuit 49. The address generation circuit 73outputs the recording/reproduction timing signal to the timing signalgeneration circuit 74. The address generation circuit 73 outputs theaddress signal and the recording/reproduction timing signal to thesystem controller 12 and the signal processor 14. The timing signalgeneration circuit 74 produces a reproduction timing signal in responseto the output signals from the PLL circuit 71 and the address detectioncircuit 73. The timing signal generation circuit 74 outputs thereproduction timing signal to the jitter signal generation circuit 56and the asymmetry detection circuit 70, thereby controlling the timingof the jitter detection by the jitter signal generation circuit 56 andthe timing of the asymmetry detection by the asymmetry detection circuit70.

The laser drive circuit 58 in the amplifier unit 26 generates a laserdrive signal. The laser drive circuit 58 outputs the laser drive signalto the semiconductor laser within the optical head 24. The semiconductorlaser emits the laser beam in response to the laser drive signal. Theoptical head 24 includes a photodiode exposed to a portion of the laserbeam emitted by the semiconductor laser. The photodiode monitors thelaser beam. The photodiode is also referred to as the monitor diode. Thephotodiode generates a signal representing the intensity (or the power)of the laser beam. The photodiode feeds the laser intensity signal backto the laser drive circuit 58 in the amplifier unit 26. The laser drivecircuit 58 controls the laser drive signal in response to the laserintensity signal. The semiconductor laser, the photodiode, and the laserdrive circuit 58 compose an APC (automatic power control) circuit forregulating the power of the laser beam at a desired level controlled bythe system controller 12. The APC can be selectively enabled anddisabled by the system controller 12. For example, the APC is enabledduring the playback mode of operation of the apparatus, and is disabledduring the recording mode of operation of the apparatus. The laser drivecircuit 58 transmits the laser intensity signal to an A/D converterwithin the system controller 12. Thus, the intensity of the laser beamcan be monitored by the system controller 12.

During the recording mode of operation of the apparatus, the timingsignal generation circuit 74 produces a timing signal. The timing signalgeneration circuit 74 outputs the timing signal to the test patterngeneration circuit 64, the system controller 12, and the signalprocessor 14. The test pattern generation circuit 64 produces a signalof a test pattern in response to the output signal from the timingsignal generation circuit 74 while being controlled by the systemcontroller 12. The test pattern generation circuit 64 outputs the testpattern signal to the switch 62. The switch 62 receives the 8-16modulation-resultant signal (the write data or the contents data to berecorded) from the signal processor 14. The switch 62 is controlled bythe system controller 12, selecting one of the test pattern signal andthe 8-16 modulation-resultant signal and outputting the selected signalto the waveform correction circuit 60.

The waveform correction circuit 60 converts the waveform of the outputsignal of the switch 62 into one of waveforms basically similar to therecording waveform WA and a waveform equivalent to the recordingwaveform WB. The waveform correction circuit 60 uses waveform correctionparameters which determine the recording power level Pp, the erasingpower level Pb, and the time intervals Ta, Tb, Tc, and Td in therecording waveform WA. At least one of the waveform correctionparameters used by the waveform correction circuit 60 can be changed sothat the waveform of the signal generated thereby can be changed amongthose basically similar to the recording waveform WA. The waveformcorrection parameters used by the waveform correction circuit 60 can bechanged by the system controller 12. The waveforms basically similar tothe recording waveform WA are different from each other. Accordingly,these waveforms provide different statuses of the power conditions (theintensity conditions) of the laser beam respectively. One of thedifferent statuses of the power conditions of the laser beam is selectedthrough the control of the waveform correction circuit 60 by the systemcontroller 12.

FIG. 29 shows an example of the waveform correction circuit 60. Thewaveform correction circuit 60 in FIG. 29 includes waveform converters60A1, 60A2, 60A3, 60A4, 60A5, 60A6, 60A7, 60A8, and 60B, and a switch60C. The input terminals of the waveform converters 60A1-60A8, and 60Bare connected to the switch 62 (see FIG. 11). The output terminals ofthe waveform converters 60A1-60A8, and 60B are connected to the switch60C. The switch 60C is connected to the laser drive circuit 58 (see FIG.11). The switch 60C has a control terminal connected to the systemcontroller 12 (see FIG. 9).

The waveform converters 60A1-60A8 in the waveform correction circuit 60change the output signal of the switch 62 into pulse train signalshaving waveforms basically similar to the recording waveform WA (seeFIG. 3). The waveform converters 60A1-60A8 output the pulse trainsignals to the switch 60C. The pulse train signals generated by thewaveform converters 60A1-60A8 are different from each other in at leastone of waveform correction parameters. The waveform correctionparameters include a parameter determining the recording power level Ppof the laser beam, a parameter determining the erasing power level Pb ofthe laser beam, a parameter determining the time interval Ta, aparameter determining the time interval Tb, a parameter determining thetime interval Tc, and a parameter determining the time interval Td (seeFIG. 3). The recording power level Pp, the erasing power level Pb, andthe time intervals Ta, Tb, Tc, and Td vary as the values of the waveformcorrection parameters change. The power conditions (the intensityconditions) of the laser beam depend on the recording power level Pp,the erasing power level Pb, and the time intervals Ta, Tb, Tc, and Td.Accordingly, the waveform converters 60A1, 60A2, 60A3, 60A4, 60A5, 60A6,60A7, and 60A8 correspond to eight different statuses P1, P2. P3, P4.P5, P6, P7, and P8 of the power conditions of the laser beam,respectively. As understood from the previous description, the waveformconverters 60A1-60A8 have respective eight different sets of thewaveform correction parameters. Each of the waveform converters60A1-60A8 may use a known circuit.

The waveform converter 60B in the waveform correction circuit 60 changesthe output signal of the switch 62 into a pulse signal having a waveformequivalent to the recording waveform WB (see FIG. 3). The waveformconverter 60B includes a pulse-width shortening circuit. Specifically,the waveform converter 60B includes a delay element and an AND circuit.The delay element defers the output signal of the switch 62. The ANDcircuit executes AND operation between the output signal of the delayelement and the output signal of the switch 62, thereby generating thepulse signal. The waveform converter 60B outputs the pulse signal to theswitch 60C.

The switch 60C in the waveform correction circuit 60 selects one fromamong the output signals of the waveform converters 60A1-60A8, and 60Bin response to a control signal fed from the system controller 12. Theswitch 60C transmits the selected signal to the laser drive circuit 58.The laser drive circuit 58 converts the selected signal into acorresponding laser drive signal. When the switch 60C selects one of theoutput signals of the waveform converters 60A1-60A8, the laser beamemitted by the semiconductor laser has a waveform basically similar tothe recording waveform WA (see FIG. 3). At this time, the powerconditions (the intensity conditions) of the laser beam agree with oneof the eight different statuses P1-P8 which corresponds to thewaveform-converter output signal selected by the switch 60C. Thus, thepower conditions of the laser beam can be changed among the eightdifferent statuses P1-P8 as the switch 60C is controlled by the systemcontroller 12 to sequentially select one of the output signals of thewaveform converters 60A1-60A8. When the switch 60C selects the outputsignal of the waveform converter 60B, the laser beam emitted by thesemiconductor laser has the recording waveform WB (see FIG. 3).

As will be made clear later, during the recording mode of operation ofthe apparatus except a short term of the execution of a waveformcorrection optimizing process, the switch 60C selects one from among theoutput signals of the waveform converters 60A1-60A8, and 60B which isdesignated by the system controller 12. The selection-object designatedsignal can be changed by the system controller 12 in response to theresults of the waveform correction optimizing process. The newdesignated one of the output signals of the waveform converters60A1-60A8, and 60B is selected by the switch 60C, and is used during therecording mode of operation of the apparatus which follows the term ofthe execution of the waveform correction optimizing process.

With reference back to FIG. 11, the switch 62 is controlled by thesystem controller 12 to provide a time base change in a great unit. Thewaveform correction circuit 60 responds to the time base change. As willbe made clear later, the waveform correction parameters which determinethe laser power levels Pp and Pb, and the time intervals Ta, Tb, Tc, andTd (see FIG. 3) and which are used by the waveform correction circuit 60are set so as to optimize the asymmetry value (or the asymmetry valueand the jitter value).

The test pattern signal generated by the test pattern generation circuit64 has the alternation of the lowest-frequency signal (thelongest-period signal) “11T” and the highest-frequency signal (theshortest-period signal) “3T” of the 8-16 modulation-resultant signal.With reference to FIG. 12, the test pattern signal is selected by theswitch 62 for a time interval corresponding to one ECC block. Test dataoriginating from the test pattern signal are recorded on an ECC blockhaving an address A2. The ECC block is composed of 16 successivesectors. The ECC block loaded with the test data is also referred to asthe test ECC block. The lowest-frequency signal “11T” is recorded on thefirst sector, that is, the B0 sector in the test ECC block. Thehighest-frequency signal “3T” is recorded on the second sector, that is,the B1 sector in the test ECC block. The lowest-frequency signal “11T”is recorded on the third sector, that is, the B2 sector in the test ECCblock. The highest-frequency signal “3T” is recorded on the fourthsector, that is, the B3 sector in the test ECC block. Similarly, thelowest-frequency signal “11T” and the highest-frequency signal “3T” arealternately recorded on the fifth and later sectors in the test ECCblock. Thus, eight sets of the lowest-frequency signal “11T” and thehighest-frequency signal “3T” are assigned to eight pairs of twosuccessive sectors, respectively. During the recording of the test data,the system controller 12 changes the switch 60C within the waveformcorrection circuit 60 so that the power conditions (the intensityconditions) of the laser beam are changed among the eight differentstatuses P1, P2, . . . , and P8. The eight power statuses P1, P2, . . ., and P8 are used for the eight sets of the lowest-frequency signal“11T” and the highest-frequency signal “3T”, respectively.

During the playback mode of operation of the apparatus, the systemcontroller 12 detects an access to the test ECC block. The timing signalgeneration circuit 74 produces timing pulses T0, T1, T2, T3, . . .corresponding to the front ends of the sectors in the test ECC blockrespectively (see FIG. 12). The asymmetry detection circuit 70 samplesand holds the output signal of the RF amplifier 50 in response to thetiming pulses T0, T1, T2, T3, . . . fed from the timing signalgeneration circuit 74. Specifically, the asymmetry detection circuit 70samples and holds a peak PDP1 and a bottom PDB1 of the lowest-frequencysignal “11T” reproduced from the B0 sector in the test ECC block. Theasymmetry detection circuit 70 samples and holds a center level PDC1 ofthe highest-frequency signal “3T” reproduced from the B1 sector in thetest ECC block. Similarly, the asymmetry detection circuit 70 samplesand holds peaks and bottoms of the lowest-frequency signals “11T” andcenter levels of the highest-frequency signals “3T” reproduced from thelater sectors in the test ECC block. Thus, a peak and a bottom PDB1 ofthe lowest-frequency signal “11T”, and a center level of thehighest-frequency signal “3T” are detected for each of the eightdifferent-power sets of the lowest-frequency signal “11T” and thehighest-frequency signal “3T”. The asymmetry detection circuit 70converts the sample-and-hold results into digital data representing thedetected asymmetries for the respective eight different-power-statussets of the lowest-frequency signal “11T” and the highest-frequencysignal “3T”. The asymmetry detection circuit 70 outputs the asymmetrydata to the system controller 12.

During the recording of contents information on the optical disc 22, thesystem controller 12 sets the disc-scanning linear velocity to one fromamong different values through the speed control of the spindle motor20. The different velocity values include 6 m/s corresponding to arecording time of about 2 hours and a high picture quality, 3 m/scorresponding to a recording time of about 4 hours and a normal picturequality, and 1.5 m/s corresponding to a recording time of about 8 hoursand a low picture quality.

According to a first example, one of the waveform converters 60A1-60A8in the waveform correction circuit 60 which provide recording waveformsbasically similar to the recording waveform WA (see FIG. 3) is selectedas an active waveform converter for disc-scanning linear velocities of1.5 m/s and 3 m/s. On the other hand, the waveform converter 60B in thewaveform correction circuit 60 which provides the recording waveform WB(see FIG. 3) is selected as an active waveform converter for adisc-scanning linear velocity of 6 m/s.

According to a second example, one of the waveform converters 60A1-60A8in the waveform correction circuit 60 which provide recording waveformsbasically similar to the recording waveform WA (see FIG. 3) is selectedas an active waveform converter for disc-scanning linear velocities of1.5 m/s, 3 m/s, and 6 m/s.

The contents-information recording time can be varied by changing notonly the disc-scanning linear velocity but also the compression datarate used by the audio-video encoding and decoding unit 30. The transferrate of the signal recorded on the optical disc 22 is set higher thanthe transfer rate of the compression-resultant data which corresponds tothe highest compression data rate. The difference between the transferrates is absorbed by the memory 28.

The CLV control of the optical disc. 22 may be replaced by CAV controlor zone CAV control. In this case, even when an inner-circumferencelinear velocity and an outer-circumference linear velocity are changedfor about 30 zones, the system controller 12 manages address positionson a recording track and sets an actual linear-velocity for each of theaddress positions. In addition, the period T of the bit clock signal isset on the basis of the set linear velocity.

With reference to FIG. 13, time intervals “a” alternate with timeintervals “b”. During the time intervals “a”, a signal is written intothe memory 28 at a first transfer rate. During the time intervals “b”,the signal is read out from the memory 28 at a second transfer ratehigher than the first transfer rate before being recorded on the opticaldisc 22. The upper side of the occupancy of the memory 28 is limited toa full level. The full level is set in response to the compression datarate or an externally applied signal. After an initial stage, the lowerside of the occupancy of the memory 28 is limited to an empty level.

The system controller 12 operates in accordance with a program stored inits internal ROM. According to the program, the system controller 12decides which of a recording mode, a playback mode, and a waiting modethe required mode of operation of the apparatus is equal to. When therequired mode is equal to the recording mode, the program advances to asegment corresponding to the recording mode. When the required mode isequal to the playback mode, the program advances to a segmentcorresponding to the playback mode. When the required mode is equal tothe waiting mode, the program advances to a segment corresponding to thewaiting mode.

FIG. 14 is a flowchart of the program segment corresponding to therecording mode. With reference to FIG. 14, a first step SB of theprogram segment activates the audio-video encoding and decoding unit 30and the signal processor 14 to generate processing-resultant contentsdata (processing-resultant audio and video data to be recorded). Thefirst step SB controls the signal processor 14 to write theprocessing-resultant contents data into the memory 28. After the stepSB, the program advances to a step SC.

The step SC decides whether or not the degree of the occupancy of thememory 28 has reached the full level. When the degree of the occupancyof the memory 28 has reached the full level, the program advances fromthe step SC to a step SD. Otherwise, the program returns from the stepSC to the step SB.

The step SD controls the signal processor 14 to read out the contentsdata from the memory 28. The step SD controls the amplifier unit 26 totransmit the readout contents data from the memory 28 to the opticalhead 24. The contents data are recorded on the optical disc 22 by theoptical head 24.

A step SE following the step SD decides whether or not the degree of theoccupancy of the memory 28 has reached the empty level. When the degreeof the occupancy of the memory 28 has reached the empty level, theprogram advances from the step SE to a step SF. Otherwise, the programreturns from the step SE to the step SD.

The step SF controls the signal processor 14 to suspend reading out thecontents data from the memory 28. After the step SF, the programadvances to a step SG.

The step SG decides whether or not a waveform correction optimizingprocess should be executed. In the case where the waveform correctionoptimizing process has not been executed yet after the placement of thepresent optical disc 22 in position within the apparatus, the step SGdecides that the waveform correction optimizing process should beexecuted. On the other hand, in the case where the waveform correctionoptimizing process has been executed, the step SG decides that thewaveform correction optimizing process should not be executed. When itis decided that the waveform correction optimizing process should beexecuted, the program advances from the step SG to a step SH. When it isdecided that the waveform correction optimizing process should not beexecuted, the program returns from the step SG to the step SC.

The step SH memorizes or stores the address of a position (an ECC block)on the optical disc 22 which should be accessed next for the recordingof the contents data.

A block SI following the step SH changes the operation of the apparatusto a test mode to execute the waveform correction optimizing process.

A step SJ subsequent to the block SI returns the operation of theapparatus to the recording mode. The step SJ controls the servoprocessor 16 in response to the address stored by the step SH so thatthe optical head 24 will kick back to the position on the optical disc22 which should be accessed next for the recording of the contents data.After the step SJ, the program returns to the step SC.

It should be noted that the step SG may be omitted from the programsegment in FIG. 14. In this case, the step SF is immediately followed bythe step SH.

As shown in FIG. 15, a first step SIa in the block SI detects theaddress of a position (an ECC block) on the optical disc 22 whichimmediately follows the address of the last accessed position loadedwith the contents data. The ECC block address A2 in FIG. 12 correspondsto the address detected by the step SIa while the ECC block address A1in FIG. 12 corresponds to the address of the last accessed positionloaded with the contents data.

A step SIb subsequent to the step SIa controls the amplifier unit 26 torecord the test pattern signal on the disc position (the ECC block)whose address is detected by the step SIa. The ECC block loaded with thetest pattern signal is also referred to as the test ECC block.Specifically, the step SIb controls the switch 62 within the amplifierunit 26 to select the test pattern signal fed from the test patterngeneration circuit 64.

As previously mentioned, the test pattern signal has the alternation ofthe lowest-frequency signal (the longest-period signal) “11T” and thehighest-frequency signal (the shortest-period signal) “3T” of the 8-16modulation-resultant signal. As shown in FIG. 12, the lowest-frequencysignal “11T” is recorded on the first sector, that is, the B0 sector inthe test ECC block. The highest-frequency signal “3T” is recorded on thesecond sector, that is, the B1 sector in the test ECC block. Thelowest-frequency signal “11” is recorded on the third sector, that is,the B2 sector in the test ECC block. The highest-frequency signal “3T”is recorded on the fourth sector, that is, the B3 sector in the test ECCblock. Similarly, the lowest-frequency signal “11T” and thehighest-frequency signal “3T” are alternately recorded on the fifth andlater sectors in the test ECC block. Thus, eight sets of thelowest-frequency signal “11T” and the highest-frequency signal “3T” areassigned to eight pairs of two successive sectors, respectively.

The step Sib controls the waveform correction circuit 60 to change thepower conditions (the intensity conditions) of the laser beam among theeight different statuses P1, P2, . . . , and P8. Specifically, the stepSib changes at least one of the waveform correction parameters in thewaveform correction circuit 60 among eight different values. As shown inFIG. 12, the eight power statuses P1, P2, . . . , and P8 are used forthe eight sets of the lowest-frequency signal “11T” and thehighest-frequency signal “3T”, respectively. The laser-beam powercondition change is accorded with one of a monotonically increasingpattern, a monotonically decreasing pattern, a pattern in which thepower level is alternately changed between a positive side and anegative side of a predetermined value, a pattern in which the powerlevel is changed in correspondence with the detected temperature, apattern in which the power level is changed with the record position,predetermined different patterns corresponding to the lapse of time fromthe previous recording, and different patterns depending on theconditions of the apparatus.

A step SIc following the step SIb controls the servo processor 16 sothat the optical head 24 will kick back to the front end of the test ECCblock on the optical disc 22. After the step SIc, the program advancesto a step SId.

A step SId changes the operation of the apparatus to the playback mode.The step SId controls the optical head 24 via the amplifier unit 26 toreproduce the test pattern signal from the test ECC block. The step SIdreceives the data from the amplifier unit 26 which represent thedetected asymmetries for the respective eight different-power-conditionsets of the lowest-frequency signal “11T” and the highest-frequencysignal “3T”. The received asymmetry data contain information of thedetected peak and the detected bottom of the lowest-frequency signal“11T”, and the center level of the highest-frequency signal “3T” foreach of the eight different-power-status sets of the lowest-frequencysignal “11” and the highest-frequency signal “3T”.

A step SIe calculates the error (the deviation or difference) of thecenter level of the highest-frequency signal “3T” from the centerbetween the detected peak and the detected bottom of thelowest-frequency signal “11T” for each of the eightdifferent-power-status sets of the lowest-frequency signal “11T” and thehighest-frequency signal “3T”. The step SIe compares the calculatederrors, and thereby detects the smallest of the calculated errors. Thestep SIe selects one from among the eight different-power-status sets ofthe lowest-frequency signal “11T” and the highest-frequency signal “3T”which corresponds to the smallest error. In other words, the step SIeselects one from among the eight different recording power statuseswhich corresponds to the smallest error. The step SIe identifies thevalue of the waveform correction parameter (or the values of thewaveform correction parameters) in the waveform correction circuit 60which corresponds to the selected one of the eight different recordingpower statuses. Specifically, the step SIe identifies one of thewaveform converters 60A1-60A8 in the waveform correction circuit 60which corresponds to the selected one of the eight different recordingpower statuses.

A step SIf subsequent to the step SIe decides whether or not theidentified value of the waveform correction parameter (or the identifiedvalues of the waveform correction parameters) is equal to the parametervalue which is currently set in the waveform correction circuit 60 forthe recording of the contents data. When the identified value is notequal to the currently-set parameter value, the program advances fromthe step SIf to a step SIg. When the identified value is equal to thecurrently-set parameter value, the program jumps from the step SIf tothe step SJ in FIG. 14. Specifically, the step SIf decides whether ornot the identified waveform converter is the same as that currently setactive for the recording of the contents data (the currently designatedwaveform converter). When the identified waveform converter is the sameas that currently set active, the program jumps from the step SIf to thestep SJ in FIG. 14. Otherwise, the program advances from the step SIf tothe step SIg.

The step SIg updates or changes the waveform correction parameter orparameters in the waveform correction circuit 60 to the identified valueor values. Specifically, the step SIg controls the switch 60C in thewaveform correction circuit 60 to select the output signal of one of thewaveform converters 60A1-60A8 which is the same as the identifiedwaveform converter. The selected waveform-converter output signal isused for later recording of the contents data. After the step SIg, theprogram advances to the step SJ in FIG. 14.

As shown in FIG. 12, the contents data are recorded on the ECC block atthe address A1 by the step SD (see FIG. 14). The test pattern signal isrecorded on the ECC block at the address A2 by the step SIb (see FIG.15). The address A2 immediately follows the address A1. The recording ofthe contents data on the ECC block at the address A1 is continuouslyfollowed by the recording of the test pattern signal on the next ECCblock at the address A2. Thus, a waiting time is prevented fromoccurring between the recording of the contents data and the subsequentrecording of the test pattern signal. As previously mentioned, the testpattern signal is reproduced from the ECC block at the address A2 toimplement the waveform correction optimizing process. Then, the opticalhead 24 is moved back to the front end of the ECC block at the addressA2. Subsequently, the contents data are recorded on the ECC block at theaddress A2 by the step SD (see FIG. 14). In this case, the contents dataare written over the test pattern signal.

A 0-kilobyte linking method is applied to the connection between thecontents data on the neighboring ECC blocks at the addresses A1 and A2.The O-kilobyte linking method may use that shown in, for example,Japanese published unexamined patent application 2000-137952 or Japanesepublished unexamined patent application 2000-137948, the disclosure ofwhich is hereby incorporated by reference. According to the 0-kilobytelinking method, the previous contents data and the new contents data arecontinuously recorded in a manner such that the connection between theprevious contents data and the new contents data is located at theboundary between two neighboring ECC blocks. The previous contents dataand the new contents data can be continuously reproduced. As previouslymentioned, the new contents data are written over the test patternsignal. Since the test pattern signal and the new contents data arerecorded in the same recording method, the test pattern signal is fullyerased by the overwriting process.

With reference back to FIG. 11, the PLL circuit 71 receives the wobblesignal from the wobble detection circuit 72. The wobble signal has afrequency of, for example, 140 kHz. The wobble signal has a waveformshown in FIG. 28. The PLL circuit 71 multiplies the frequency of thewobble signal, thereby generating the recording clock signal having afrequency equal to an integer multiple of the wobble signal frequency(see FIG. 28). The frequency of the recording clock signal is equal to,for example, 27 MHz. The timing signal generation circuit 74 receivesthe recording clock signal from the PLL circuit 71. Also, the timingsignal generation circuit 74 receives the recording/reproduction timingsignal (the LPP signal) from the address detection circuit 73. The LPPsignal has a waveform shown in FIG. 28. A 1-sync-frame correspondingsignal is recorded on the optical disc 22 in synchronism with the LPPsignal. The timing signal generation circuit 74 counts pulses in therecording clock signal while using a timing given by the LPP signal as areference. Thereby, the timing signal generation circuit 74 producestiming pulses T0, T1, T2, T3, . . . corresponding to the front ends ofthe sectors in the test ECC block respectively (see FIG. 12). The timingsignal generation circuit 74 outputs the timing pulses T0, T1, T2, T3, .. . to the asymmetry detection circuit 70 as a reproduction timingsignal. The timing signal outputted from the timing signal generationcircuit 74 has a waveform shown in FIG. 28.

As shown in FIG. 16, the asymmetry detection circuit 70 includes a peakhold circuit 601, a bottom hold circuit 602, a low pass filter (an LPF)603, an A/D converter 604, and a switch 605. The peak hold circuit 601,the bottom hold circuit 602, and the LPF 603 receive the output signalof the RF amplifier 50. The peak hold circuit 601, the bottom holdcircuit 602, the LPF 603, and the switch 605 receive the reproductiontiming signal (the timing pulses) from the timing signal generationcircuit 74.

The peak hold circuit 601 and the bottom hold circuit 602 are reset atthe moment given by the timing pulse T0 (see FIG. 12). The peak holdcircuit 601 holds the peak level of the lowest-frequency signal “11T”which is reproduced from the first sector, that is, the B0 sector in thetest ECC block during the time interval between the moments given thetiming pulses T0 and T1 (see FIG. 12). The peak hold circuit 601 outputsa signal representative of the held peak level to the switch 605. Thebottom hold circuit 602 holds the bottom level of the lowest-frequencysignal “11T” which is reproduced from the first sector in the test ECCblock. The bottom hold circuit 602 outputs a signal representative ofthe held bottom level to the switch 605. The LPF 603 smooths or averagesthe highest-frequency signal “3T” which is reproduced from the secondsector, that is, the B1 sector in the test ECC block during the timeinterval between the moments given by the timing pulses T1 and T2 (seeFIG. 12). Thus, the LPF 603 generates a signal representing the centerlevel of the highest-frequency signal “3T” reproduced from the secondsector in the test ECC block. The LPF 603 outputs the center levelsignal to the switch 605. During a short time interval at and around themoment given by the timing pulse T2, the switch 605 sequentially selectsand transmits the peak level signal, the bottom level signal, and thecenter level signal to the A/D converter 604. The A/D converter 604changes the peak level signal, the bottom level signal, and the centerlevel signal into corresponding digital data. The A/D converter 604outputs the digital data to the system controller 12. In this way, thepeak level, the bottom level, and the center level are detected and arenotified to the system controller 12 for first one of the eightdifferent-power-status sets of the lowest-frequency signal “11T” and thehighest-frequency signal “3T”. Similarly, the peak level, the bottomlevel, and the center level are detected and are notified to the systemcontroller 12 for second and later ones of the eightdifferent-power-status sets of the lowest-frequency signal “11T” and thehighest-frequency signal “3T”.

According to the first embodiment of this invention, during a free timeof the optical head 24 in the term of writing contents data into thememory 28, the test pattern signal is recorded on and reproduced from adisc position to be accessed next for the recording of the contentsdata. The asymmetry of the reproduced test pattern signal is measured.The waveform correction parameters which determine the intensity (thepower) of the laser beam are set and adjusted so as to optimize themeasured asymmetry. Thus, the optimal conditions of the signal recordingon the disc position to be accessed next are detected on a measurementbasis. In some cases, the recording sensitivity of the optical disc 22varies from disc position to disc position. Therefore, in these cases,the optical recording conditions vary from disc position to discposition. In the first embodiment of this invention, it is possible todetect the optimal recording conditions at each of varying discpositions. As previously mentioned, the test patten signal is erasedsince the new contents data are written thereover. Therefore, it isunnecessary to provide an exclusive disc area for storing the testpattern signal. Furthermore, it is unnecessary for the optical head 24to implement seek to the exclusive disc area for storing the testpattern signal. In addition, it is unnecessary to provide a special timeof setting and adjusting the waveform correction parameters.

Second Embodiment

A second embodiment of this invention is a modification of the firstembodiment thereof. The second embodiment of this invention uses a blockSGA instead of the step SG in FIG. 14.

As shown in FIG. 17, the block SGA has a first-step 01 following thestep SF (see FIG. 14). The step 101 decides whether or not a timer valueis smaller than a predetermined value “k”. When the timer value is notsmaller than the predetermined value “k”, that is, when the timer valueis equal to or greater than the predetermined value “k”, the programadvances from the step 101 to a step 102. When the timer value issmaller than the predetermined value “k”, the program advances from thestep 101 to a step 103.

The step 102 resets the timer value. After the step 102, the programadvances to the step SH (see FIG. 14).

The step 103 counts up or increments the timer value by “1”. After thestep 103, the program returns to the step SC (see FIG. 14).

Third Embodiment

A third embodiment of this invention is a modification of the firstembodiment thereof. The third embodiment of this invention uses a blockSGB instead of the step SG in FIG. 14.

As shown in FIG. 18, the block SGB has a first step 201 following thestep SF (see FIG. 14). The step 201 decides whether or not the addressof a new ECC block for data recording is separate from the address of alast test ECC block by at least a predetermined distance (apredetermined address value). When the address of the new ECC block isseparate from the address of the last test ECC block by at least thepredetermined distance, the program advances from the step 201 to a step202. Otherwise, the program returns from the step 201 to the step SC(see FIG. 14).

The step 202 stores the address of the new ECC block as the address of anewest ECC block. After the step. 202, the program advances to the stepSH (see FIG. 14).

Fourth Embodiment

A fourth embodiment of this invention is a modification of the firstembodiment thereof. The fourth embodiment of this invention uses a blockSGC instead of the step SG in FIG. 14.

As shown in FIG. 19, the block SGC has a first step 301 following thestep SF (see FIG. 14). The step 301 decides whether or not the presenttemperature is separate from the temperature, which occurs at the lastexecution of the waveform correction optimizing process, by at least apredetermined value. When the present temperature is separate from thetemperature, which occurs at the last execution of the waveformcorrection optimizing process, by at least the predetermined value, theprogram advances from the step 301 to a step 302. Otherwise, the programreturns from the step 301 to the step SC (see FIG. 14).

The step 302 stores information of the present temperature as thetemperature which occurs at the new execution of the waveform correctionoptimizing process. After the step 302, the program advances to the stepSH (see FIG. 14).

Fifth Embodiment

A fifth embodiment of this invention is a modification of the firstembodiment thereof. The fifth embodiment of this invention uses a blockSGD instead of the step SG in FIG. 14.

As shown in FIG. 20, the block SGD has a first step 401 following thestep SF (see FIG. 14). The step 401 kicks the optical head 24 back tothe front end of the last accessed ECC block.

A step 402 following the step 401 reproduces a signal from the ECCblock. The step 402 detects jitter of the reproduced signal.

A step 403 subsequent to the step 402 decides whether or not thedetected jitter exceeds a predetermined value. When the detected jitterexceeds the predetermined value, the program advances from the step 403to the step SH (see FIG. 14). Otherwise, the program returns from thestep 403 to the step SC (see FIG. 14).

Sixth Embodiment

A sixth embodiment of this invention is a modification of the firstembodiment thereof. The sixth embodiment of this invention uses a blockSGE instead of the step SG in FIG. 14.

As shown in FIG. 21, the block SGE has a first step 401A following thestep SF (see FIG. 14). The step 401A kicks the optical head 24 back tothe front end of the last accessed ECC block.

A step 402A following the step 401A reproduces data from the ECC block.The step 402A detects the error rate of the reproduced data.

A step 403A subsequent to the step 402A decides whether or not thedetected error rate exceeds a predetermined value. When the detectederror rate exceeds the predetermined value, the program advances fromthe step 403A to the step SH (see FIG. 14). Otherwise, the programreturns from the step 403A to the step SC (see FIG. 14).

Seventh Embodiment

A seventh embodiment of this invention is a modification of the firstembodiment thereof. The seventh embodiment of this invention uses ablock SGF instead of the step SG in FIG. 14.

As shown in FIG. 22, the block SGF has a first step 501 following thestep SF (see FIG. 14). The step 501 decides whether or not the presentvoltage of the feedback signal from the monitor diode is different fromthe feedback signal voltage, which occurs at the last execution of thewaveform correction optimizing process, by at least a predeterminedvalue. When the present voltage of the feedback signal is different fromthe feedback signal voltage, which occurs at the last execution of thewaveform correction optimizing process, by at least the predeterminedvalue, the program advances from the step 501 to a step 502. Otherwise,the program returns from the step 501 to the step SC (see FIG. 14).

The step 502 stores information of the present voltage of the feedbacksignal as the feedback signal voltage which occurs at the new executionof the waveform correction optimizing process. After the step 502, theprogram advances to the step SH (see FIG. 14).

Eighth Embodiment

An eighth embodiment of this invention is a combination of the secondand third embodiments thereof. In the eighth embodiment of thisinvention, the waveform correction optimizing process is executed whenthe step 101 decides that the timer value is equal to or greater thanthe predetermined value “k” or when the step 201 decides that theaddress of the new ECC block is separate from the address of the lasttest ECC block by at least the predetermined distance.

Ninth Embodiment

A ninth embodiment of this invention is a combination of the second,third, fourth, fifth, sixth, and seventh embodiments thereof. In theninth embodiment of this invention, the waveform correction optimizingprocess is executed only when at least one of the following conditions1), 2), 3), 4), 5), and 6) is satisfied.

-   1) The step 101 decides that the timer value is equal to or greater    than the predetermined value “k”.-   2) The step 201 decides that the address of the new ECC block is    separate from the address of the last test ECC block by at least the    predetermined distance.-   3) The step 301 decides that the present temperature is separate    from the temperature, which occurs at the last execution of the    waveform correction optimizing process, by at least the    predetermined value.-   4) The step 403 decides that the detected jitter exceeds the    predetermined value.-   5) The step 403A decides that the detected error rate exceeds the    predetermined value.-   6) The step 501 decides that the present voltage of the feedback    signal is different from the feedback signal voltage, which occurs    at the last execution of the waveform correction optimizing process,    by at least the predetermined value.

Tenth Embodiment

A tenth embodiment of this invention is a combination of the second andthird embodiments thereof. In the tenth embodiment of this invention,the waveform correction optimizing process is executed only when boththe following conditions 1) and 2) are satisfied.

-   1) The step 101 decides that the timer value is equal to or greater    than the predetermined value “k”.-   2) The step 201 decides that the address of the new ECC block is    separate from the address of the last test ECC block by at least the    predetermined distance.

Eleventh Embodiment

An eleventh embodiment of this invention is a combination of the second,third, and fourth embodiments thereof. In the eleventh embodiment ofthis invention, the waveform correction optimizing process is executedonly when at least one of the following conditions 1) and 2) aresatisfied.

-   1) The step 101 decides that the timer value is equal to or greater    than the predetermined value “k”. The step 201 decides that the    address of the new ECC block is separate from the address of the    last test ECC block by at least the predetermined distance.-   2) The step 101 decides that the timer value is equal to or greater    than the predetermined value “k”. The step 301 decides that the    present temperature is separate from the temperature, which occurs    at the last execution of the waveform correction optimizing process,    by at least the predetermined value.

Twelfth Embodiment

A twelfth embodiment of this invention is a combination of at least twoof the second, third, fourth, fifth, sixth, and seventh embodimentsthereof.

Thirteenth Embodiment

A thirteenth embodiment of this invention is a modification of one ofthe first to twelfth embodiments thereof. In the thirteenth embodimentof this invention, the peak level of the lowest-frequency signal “11T”reproduced from one sector in the test ECC block is sampled and held ateach of different time points. The sampled and held peak levels areaveraged into a mean peak level. The mean peak level is notified to thesystem controller. Similarly, the bottom level of the lowest-frequencysignal “11T” reproduced from one sector in the test ECC block is sampledand held at each of different time points. The sampled and held bottomlevels are averaged into a mean bottom level. The mean bottom level isnotified to the system controller.

The thirteenth embodiment of this invention compensates for a variationin the conditions of the 1-sector-corresponding reproduced signal whichmight be caused by noise in the apparatus, unevenness in the sensitivityof the optical disc 22, and a change in the tracking servo conditions.Therefore, the thirteenth embodiment of this invention accuratelymeasures or detects the asymmetry.

Fourteenth Embodiment

A fourteenth embodiment of this invention is a modification of one ofthe first to thirteenth embodiments thereof. The fourteenth embodimentof this invention measures the jitter instead of the asymmetry. The testpattern signal may be a random signal or a portion of the contents data.

In the fourteenth embodiment of this invention, the test pattern signalis recorded on a test ECC block while the power conditions or theintensity conditions of the laser beam (at least one of the waveformcorrection parameters in the waveform correction circuit 60) are changed2-sector by 2-sector. The test pattern signal is reproduced from thetest ECC block. The jitter of the reproduced signal is measured at atiming similar to the previously-indicated timing for each of the sectorpairs. The smallest of the measured jitters is selected. From among theeight different power conditions (statuses), one is selected whichcorresponds to the smallest jitter. The selected one of the eightdifferent power statuses is used as an optimal power status. Thewaveform correction parameter or parameters in the waveform correctioncircuit 60 are changed in accordance with the optimal power status. Thechange of the waveform correction parameter or parameters may beimplemented by using a predetermined correction coefficient orcoefficients in a table corresponding to the characteristics of theoptical disc 22.

Fifteenth Embodiment

A fifteenth embodiment of this invention is a modification of one of thefirst to fourteenth embodiments thereof. In the fifteenth embodiment ofthis invention, during the test mode of operation of the apparatus, alaser beam whose power changes between at least two different levels(for example, a recording level and an erasing level) is applied to agiven-address position on the optical disc 22.

In the case where the optical disc 22 is of the phase change rewritabletype, the power of the laser beam may change among a reproducing level,an erasing level, and a recording level. In the case where the opticaldisc 22 is of the organic-dye recordable type, the power of the laserbeam may change between a reproducing level and a recording level.

The feedback signal outputted from the monitor diode indicates themeasured power (the measured intensity) of the laser beam. The feedbacksignal is converted into corresponding digital data. The systemcontroller 12 derives, from the digital data, the measured valuescorresponding to the different power levels respectively. The systemcontroller 12 calculates the errors between the measured values andoptimal values. The system controller 12 controls the actual powerlevels of the laser beam so as to move the measured values toward theoptical values.

The fifteenth embodiment of this invention compensates for a variationin the laser power (the laser intensity) which might be caused by thetemperature dependency and the ageing of the semiconductor laser.

The control in the fifteenth embodiment of this invention may becombined with the previously-mentioned control based on the asymmetrymeasurement or the jitter measurement.

The fifteenth embodiment of this invention uses a block SIZ instead ofthe block SI in FIGS. 14 and 15.

As shown in FIG. 23, the block SIZ has a first step SIA following thestep SH (see FIG. 14). The step SIA detects the address of a position(an ECC block) on the optical disc 22 which immediately follows theaddress of the last accessed position loaded with the contents data; TheECC block address A2 in FIG. 12 corresponds to the address detected bythe step SIA while the ECC block address A1 in FIG. 12 corresponds tothe address of the last accessed position loaded with the contents data.

A step SIB subsequent to the step SIA controls the amplifier unit 26 torecord the test pattern signal on the disc position (the ECC block)whose address is detected by the step SIA. During the recording of thetest pattern signal, the step SIB changes the power or the intensity ofthe laser beam between at least two different levels. The step SIBderives from the feedback signal outputted by the monitor diode, themeasured values corresponding to the different power levelsrespectively. The step SIB calculates the errors between the measuredvalues and optimal values.

A step SIC following the step SIB decides whether or not a set of thecalculated errors is in a predetermined acceptable range. When the setof the calculated errors is in the acceptable range, the programadvances from the step SIC to the step SJ (see FIG. 14). When the set ofthe calculated errors is not in the acceptable range, the programadvances from the step SIC to a step SID.

The step SID outputs a control signal to the waveform correctioncircuit, thereby changing the waveform correction parameter orparameters in the direction of moving the measured power values towardthe optimal power values. After the step SID, the program advances tothe step SJ (see FIG. 14).

Sixteenth Embodiment

A sixteenth embodiment of this invention is a modification of one of thefirst to fifteenth embodiments thereof. According to the sixteenthembodiment of this invention, during every free time of the optical head24 in the recording mode of operation of the apparatus, the waveformcorrection optimizing process is implemented.

Seventeenth Embodiment

A seventeenth embodiment of this invention is a modification of one ofthe first to sixteenth embodiments thereof. The seventeenth embodimentof this invention executes the waveform correction optimizing processwithout deciding whether or not the waveform correction optimizingprocess should be executed.

Eighteenth Embodiment

An eighteenth embodiment of this invention is a modification of one ofthe first to seventeenth embodiments thereof. The eighteenth embodimentof this invention changes the waveform correction parameters fordetermining the time intervals Ta, Tb, Tc, and Td in accordance with thetemperature measured by the temperature sensor 36. For example, when themeasured temperature is 10° C., the waveform correction parameters arechanged so that the time interval Td will be increased relative to thetime interval Tc. When the measured temperature is 40° C., the waveformcorrection parameters are changed so that the time interval Tc will beincreased relative to the time interval Td.

Nineteenth Embodiment

A nineteenth embodiment of this invention is a modification of one ofthe first to eighteenth embodiments thereof. According to the nineteenthembodiment of this invention, during the test mode of operation of theapparatus, the highest-frequency signal “3T” is extracted from thereproduced RF signal. The waveform correction parameters in the waveformcorrection circuit 60 are controlled so as to maximize the amplitude ofthe highest-frequency signal “3T”.

Twentieth Embodiment

A twentieth embodiment of this invention is a modification of one of thefirst to nineteenth embodiments thereof. In the twentieth embodiment ofthis invention the waveform correction optimizing process uses thejitter instead of the asymmetry. The twentieth embodiment of thisinvention includes a suitable circuit for counting the number of timesof recording in connection with the recording track. The number of timesof recording is incremented by “1” each time recording is executed. Theeight different statuses P1, P2, . . . , and P8, among which the powerconditions of the laser beam are changed, are varied in the direction ofincreasing the acceptable limit jitter value as the number of times ofrecording increases. It is preferable to change the time intervals Ta,Tb, Tc, and Td on a stepwise basis. The twentieth embodiment of thisinvention compensates for an adverse change in jitter due to an increasein the number of times of recording.

Twenty-First Embodiment

A twenty-first embodiment of this invention is a modification of one ofthe first to twentieth embodiments thereof. In the twenty-firstembodiment of this invention, every signal pulse is shaped into a trainof short pulses based on the recording waveform WA independent of thedisc-scanning linear velocity. The amplitude of the pulse train (forexample, the amplitude of a front end portion of the pulse train) ischanged in accordance with the disc-scanning linear velocity. Thetwenty-first embodiment of this invention can provide a relatively greatphase margin.

Twenty-Second Embodiment

A twenty-second embodiment of this invention is a modification of one ofthe first to twenty-first embodiments thereof. In the twenty-secondembodiment of this invention, every signal pulse is shaped into a trainof short pulses based on the recording waveform WA independent of thedisc-scanning linear velocity. The width of the short pulses in thetrain is changed in accordance with the disc-scanning linear velocity.

The twenty-second embodiment of this invention changes the laser beambetween a recording waveform WE of FIG. 24 and a recording waveform WFof FIG. 25 in accordance with the disc-scanning linear velocity. Asshown in FIG. 24, the recording waveform WE has a train of a first pulseand later pulses with a relatively small width. As shown in FIG. 25, therecording waveform WF has a train of a first pulse and later pulses witha relatively large width. The recording waveform WE is used for a lowlinear velocity while the recording waveform WE is used for a highlinear velocity. Since the heat accumulation effect is weaker as thedisc-scanning linear velocity rises, the large-width pulses in therecording waveform WF are prevented from causing an unwanted distortionin the shape of a recording mark.

The recording waveforms WE and WF may be modified as the recordingwaveform WC of FIG. 7 is designed. Specifically, in the modifications ofthe recording waveforms WE and WF, during a limited time intervalimmediately preceding each pulse train and a limited time intervalimmediately following the pulse train, the power of the laser beam islower than the erasing level Pb.

The recording waveforms WE and WF may be modified as the recordingwaveform WD of FIG. 8 is designed. Specifically, according to themodifications of the recording waveforms WE and WF, in each pulse train,the power of a laser beam changes between a recording level Pp and areproducing level (or a null level).

Twenty-Third Embodiment

A twenty-third embodiment of this invention is a modification of one ofthe first to twenty-second embodiments thereof. The twenty-thirdembodiment of this invention is designed to properly operate on apartial ROM disc, a hybrid optical disc having an inner portion forminga ROM area and an outer portion forming a phase change RAM area, atwo-layer optical disc having one phase change recording film, atwo-layer optical disc having two phase change recording films, atwo-layer optical disc having one read only layer, or an optical dischaving two or more layers.

The twenty-third embodiment of this invention includes a device fordetecting a multi-layer optical disc, a device for detecting that atleast one layer of a multi-layer optical disc is a recordable layer (ora rewritable layer), and a focus Jump device for focusing the laser beamon the signal surface of selected one of layers in a multi-layer opticaldisc. In the twenty-third embodiment of this invention, the waveformcorrection values for the layers are decided during the test mode ofoperation of the apparatus, and the signals of the decided waveformcorrection values are stored.

Twenty-Fourth Embodiment

A twenty-fourth embodiment of this invention is a modification of one ofthe first to twenty-third embodiments thereof. The twenty-fourthembodiment of this invention provides an optical disc drive apparatuswhich does not have any signal compressing/expanding circuit. Examplesof the optical disc drive apparatus are computer peripheral apparatusessuch as a DVD-RAM drive apparatus and a DVD-RW drive apparatus.

Compressed data are outputted from the optical disc drive apparatus toan external computer without being expanded. Then, the compressed dataare expanded in the external computer according to software. The opticaldisc drive apparatus and the external computer are connected by a busof, for example, an ATAPI type or a IEEE1394 type.

In the optical disc drive apparatus, a suitable device monitors thestate of the optical head 24, and decides which of a recording state, areproducing state, a seek state, a busy state, and an unselected statethe optical head 24 assumes. When the optical head 24 falls into theunselected state, the waveform correction optimizing process isexecuted.

When the drive of the optical disc 22 has been started, the type of theoptical disc 22 is decided on the basis of the conditions of discinsertion and the conditions of turning on the power supply.Specifically, a decision is made as to whether the optical disc 22 has asingle layer or multiple layers. In addition, a decision is made as towhether or not the optical disc 22 has a recordable layer (a rewritablelayer). In the case where the optical disc 22 has a recordable layer (arewritable layer), a decision is made as to whether or the waveformcorrection optimizing process should be executed.

For example, a flag is used as an indication of whether or the waveformcorrection opt mg process should be executed. The flag in a logic stateof “0” indicates that the waveform correction optimizing process shouldbe executed. The flag in a logic state of “1” indicates that thewaveform correction optimizing process should not be executed. When thepower supply is turned on or the optical disc 22 is inserted into theapparatus, the flag is in a logic state of “0”. Thus, at this time, byreferring to the flag, it is decided that the waveform correctionoptimizing process should be executed. Therefore, the waveformcorrection optimizing process is actually executed. Then, the flag ischanged to a logic state of “1”.

When a predetermined time has elapsed since the moment of the lastexecution of the waveform correction optimizing process, the flag isreturned to a logic state of “0”. When the present temperature differsfrom that occurring at the moment of the last execution of the waveformcorrection optimizing process by more than a predetermined value, theflag is returned to a logic state of

In the case where the optical disc 22 has a recordable layer (arewritable layer), detection is given of whether or not the optical head24 falls into the unselected state. When the flag is in a logic state of“0” and the optical head 24 falls into the unselected state, thewaveform correction optimizing process is executed.

The optical disc drive apparatus includes a focus jump device forfocusing the laser beam on the signal surface of selected one of layersin the optical disc 22. In the optical disc drive apparatus, thewaveform correction values for the layers are decided during the testmode of operation of the apparatus, and the signals of the decidedwaveform correction values are stored.

Twenty-Fifth Embodiment

A twenty-fifth embodiment of this invention is a modification of one ofthe first to twenty-fourth embodiments thereof. In the twenty-fifthembodiment of this invention, the optical disc 22 is of the DVD type. Aninnermost portion of the optical disc has a lead-in area. The outer edgeof the innermost portion of the optical disc has a radius of 24 mm. Amajor portion of the optical disc 22 which extends radially outward ofthe innermost portion is used as a data area.

The lead-in area of the optical disc 22 stores physical informationrepresenting the disc type, the layer condition, the reflectivity, thedata start address, and the data end address. The disc type means theread only type, the write once type, or the rewritable type. The layercondition means the single-layer disc, the two-layer disc, “parallel”,or “opposite”. The reflectivity is equal to 0.7 in the case of thesingle-layer disc. The reflectivity is equal to 0.3 in the case of thetwo-layer disc.

In addition, the lead-in area of the optical disc 22 stores thefollowing information pieces {circle around (1)}-{circle around (6)}.The information piece {circle around (1)} indicates the optimalrecording power level Pp and the optimal erasing power level Pb of thelaser beam (see FIG. 3). The information piece {circle around (2)}indicates the optimal time intervals Ta, Tb, Tc, and Td (see FIG. 3).The information piece {circle around (2)} may indicate the optimalvalues of the waveform correction parameters in the waveform correctioncircuit 60 which determine the time intervals Ta, Tb, Tc, and Td. Theinformation piece {circle around (3)} indicates the disc-scanning linearvelocity and the temperature at which the waveform correction optimizingprocess was executed. The information piece {circle around (4)}indicates the identification code word (ID) of the recording apparatus.The information piece {circle around (5)} indicates the disc maker. Theinformation piece {circle around (5)} may further indicate the maker ofthe recording apparatus. The information piece {circle around (6)}indicates the production lot number of the disc. The information piece{circle around (6)} may further indicate the disc maker and therecording apparatus maker.

The lead-in area of the optical disc 22 may store an encrypted versionof the information pieces {circle around (1)}-{circle around (6)}. Inthe case where the optical disc 22 has two or more layers, only one ofthe layers may store the information pieces {circle around (1)}-{circlearound (6)}.

The lead-in area of the optical disc 22 includes a test recording areaon which the test pattern signal is recorded during the waveformcorrection optimizing process. The test recording area may be locatedoutside the lead-in area.

When the optical disc 22 is placed in the apparatus and the drive of theoptical disc 22 is started, a signal is reproduced from the lead-in areathereof. The information pieces {circle around (1)}-{circle around (6)}are extracted from the reproduced signal. During later recording, theapparatus uses the optimal waveform correction values indicated by theinformation pieces {circle around (1)} and {circle around (2)}. Theoptimal waveform correction values mean the optimal recording powerlevel Pp and the optimal erasing power level Pb of the laser beam, andthe optimal time intervals Ta, Tb, Tc, and Td. The optimal waveformcorrection values may mean the optimal values of the waveform correctionparameters in the waveform correction circuit 60 which determine thetime intervals Ta, Tb, Tc, and Td. The way of use of the optimalwaveform correction values is changed in response to the disc maker, thereproduction lot number of the disc, and the recording apparatus makerindicated by the information pieces {circle around (5)}and {circlearound (6)}. On the other hand, in the absence of the information pieces{circle around (1)} and {circle around (2)} from the reproduced signal,the waveform correction optimizing process is executed to determine theoptimal waveform correction values (the optimal values of the waveformcorrection parameters). Signals of the optimal waveform correctionvalues are encoded into the information pieces {circle around (1)} and{circle around (2)}. Then, the information pieces {circle around (1)}and {circle around (2)} are recorded on the lead-in area of the opticaldisc 22.

During the execution of the waveform correction optimizing process, thetemperature is measured via the temperature sensor 36. A signal of themeasured temperature and a signal of the disc-scanning linear velocityare encoded into the information piece {circle around (3)}. Theinformation piece {circle around (3)} is recorded on the lead-in area ofthe optical disc 22 while the information pieces {circle around (1)} and{circle around (2)} are recorded thereon.

As previously mentioned, when the optical disc 22 is placed in theapparatus and the drive of the optical disc 22 is started, a signal isreproduced from the lead-in area thereof. The information pieces {circlearound (1)}-{circle around (6)} are extracted from the reproducedsignal. Immediately before the start of later recording, the temperatureis measured via the temperature sensor 36. Calculation is made as to thedifference between the present temperature and the temperature indicatedby the information piece {circle around (3)}. Also, calculation is madeas to the difference between the currently-set linear velocity and thelinear velocity indicated by the information piece {circle around (3)}.The optimal waveform correction values (the optimal values of thewaveform correction parameters) are revised on the basis of thecalculated temperature difference and the calculated linear-velocitydifference according to a calculation process or a table look-upprocess. The revision-resultant optimal waveform correction values areused in later recording.

Twenty-Sixth Embodiment

A twenty-sixth embodiment of this invention is a modification of thetwenty-fifth embodiment thereof. In the twenty-sixth embodiment of thisinvention, the optical disc 22 has first and second recording layers.The first recording layer includes a specified area for storing thephysical information, the information pieces {circle around (1)}-{circlearound (6)}related to the first recording layer, and the informationpieces {circle around (1)}-{circle around (6)}related to the secondrecording layer.

When the optical disc 22 is placed in the apparatus and the drive of theoptical disc 22 is started, a signal is reproduced from the specifiedarea of the first recording layer thereof. The information pieces{circle around (1)}-{circle around (6)} related to the first recordinglayer, and the information pieces {circle around (1)}-{circle around(6)} related to the second recording layer are extracted from thereproduced signal. During later recording on the first recording layerof the optical disc 22, the apparatus uses the optimal waveformcorrection values indicated by the information pieces {circle around(1)} and {circle around (2)} related to the first recording layer.During later recording on the second recording layer of the optical disc22, the apparatus uses the optimal waveform correction values indicatedby the information pieces {circle around (1)} and {circle around (2)}related to the second recording layer. On the other hand, in the absenceof the two-layer-related information pieces {circle around (1)} and{circle around (2)} from the reproduced signal, the waveform correctionoptimizing process is executed on the first recording layer to determinethe optimal waveform correction values (the optimal values of thewaveform correction parameters) related to the first recording layer.Then, focus jump to the second recording layer is implemented, and thewaveform correction optimizing process is executed on the secondrecording layer to determine the optimal waveform correction valuesrelated to the second recording layer. Signals of the optimal waveformcorrection values related to the first and second recording layers areencoded into the two-layer-related information pieces {circle around(1)} and {circle around (2)}. Then, the two-layer-related informationpieces {circle around (1)} and {circle around (2)} are recorded on thespecified area of the first recording layer of the optical disc 22.

Twenty-Seventh Embodiment

A twenty-seventh embodiment of this invention is based on a combinationof at least two of the first to twenty-sixth embodiments thereof. Thetwenty-seventh embodiment of this invention selectively uses at leastone of the evaluation method “A”, the evaluation method “B”, and theevaluation method “C” as a part of the waveform correction optimizingprocess.

In the evaluation method “A”, the test pattern signal having thealternation of the lowest-frequency signal “11T” and thehighest-frequency signal “3T” is recorded on the optical disc 22, andthe test pattern signal is reproduced therefrom. The asymmetries ofrespective time segments of the reproduced test pattern signal aremeasured.

In the evaluation method “B”, the random signal is recorded on theoptical disc 22 as the test pattern signal, and the random signal isreproduced therefrom. The jitters of the reproduced random signal aremeasured.

In the evaluation method “C”, the feedback signal outputted from themonitor diode is measured while the power of the laser beam is changedamong the reproducing level, the erasing level, and the recording level.

FIG. 26 is a flowchart of a segment of a program for the systemcontroller 12. The program segment in FIG. 26 is executed when the driveof the optical disc 22 is started. With reference to FIG. 26, a firststep SKa of the program segment detects the type of the optical disc 22.For example, the step SKa measures the reflectivity of the optical disc22, and decides the type of the optical disc 22 on the basis of themeasured reflectivity.

A step SKb following the step SKa selects at least one from among theevaluation methods “A”, “B”, and “C”. The step SKb executes the waveformcorrection optimizing process in accordance with the selected evaluationmethod (or the selected evaluation methods).

In the case where the type of the optical disc 22 is the DVD-RW type(the phase change rewritable type), the evaluation methods “B” and “C”are selected. In this case, only the evaluation method “B” may beselected. In the case where the type of the optical disc 22 is the DVD-Rtype (the organic-dye recordable type), the evaluation methods “A” and“C” are selected. In this case, only the evaluation method “A” may beselected.

Twenty-Eighth Embodiment

A twenty-eighth embodiment of this invention is a modification of thetwenty-seventh embodiment thereof. In the twenty-eighth embodiment ofthis invention, when a disc position to be accessed at this time isseparate from the disc position previously accessed for data recordingby shorter than a predetermined distance, the evaluation method “C” isselected. When the lapse of time since the previous recording is shorterthan a predetermined time interval, the evaluation method “C” isselected. When a disc position to be accessed at this time is separatefrom the disc position previously accessed for data recording by atleast the predetermined distance, the evaluation method “A” or “B” isselected. When the lapse of time since the previous recording is equalto or longer than the predetermined time interval, the evaluation method“A” or “B” is selected.

Twenty-Ninth Embodiment

A twenty-ninth embodiment of this invention is a modification of thetwenty-seventh embodiment thereof. In the twenty-ninth embodiment ofthis invention, the optical disc 22 has a specified area for storingdisc intrinsic information (disc ID information). The disc intrinsicinformation represents the disc maker, the disc type, the disc articlenumber, and the disc production lot number. The memory in the systemcontroller 12 stores a table signal indicating the relation of the discintrinsic information with the evaluation methods “A”, “B”, and “C”.

FIG. 27 is a flowchart of a segment of a program for the systemcontroller 12. The program segment in FIG. 27 is executed when the driveof the optical disc 22 is started. With reference to FIG. 27, a firststep SKA of the program segment reproduces a signal from the specifiedarea of the optical disc 22.

A step SKB following the step SKA extracts the disc intrinsicinformation from the reproduced signal.

A step SKC subsequent to the step SKB selects at least one from amongthe evaluation methods “A”, “B”, and “C” by referring to the tablesignal. The step SKC executes the waveform correction optimizing processin accordance with the selected evaluation method (or the selectedevaluation methods).

Thirtieth Embodiment

A thirtieth embodiment of this invention is a modification of one of thefirst to twenty-ninth embodiments thereof. In the thirtieth embodimentof this invention, the test pattern generation circuit 64 is designed sothat the test pattern signal can be shifted along a time base relativeto the test ECC block by a variable quantity (a variable time interval).The shift quantity may be fixed to, for example, about 6 bytes measuredin unit of the recording clock signal (the bit clock signal). The shiftquantity may be variable in a range around 6 bytes measured in unit ofthe recording clock signal.

The shift quantity can be set by the system controller 12. In the casewhere the test pattern signal is recorded on an area of the optical disc22 for the first time, the system controller 12 sets the shift quantityto “0”. In the case where the test pattern signal is recorded again onan area of the optical disc 22 which was loaded with the test patternsignal, the system controller 12 generates a random signal. The systemcontroller 12 sets the shift quantity to the random value represented bythe random signal. The test pattern signal is shifted by the quantityset by the system controller 12. The test pattern signal is recorded.The test pattern signal is reproduced at timings shifted from theoriginal timings by a quantity corresponding to the quantity set by thesystem controller 12. The asymmetries of respective time segments of thereproduced test pattern signal are measured.

Thirty-First Embodiment

A thirty-first embodiment of this invention is a modification of one ofthe first to thirtieth embodiments thereof. In the thirty-firstembodiment of this invention, the test pattern generation circuit 64 isdesigned so that the lowest-frequency signal “11T” and thehighest-frequency signal “3T” can be exchanged in time position in thetest pattern signal.

In the case where the test pattern signal is recorded on an area of theoptical disc 22 for the first time, the lowest-frequency signal “11T”and the highest-frequency signal “3T” are arranged in the test patternsignal in the order shown in FIG. 12. In the case where the test patternsignal is recorded again on an area of the optical disc 22 which wasloaded with the test pattern signal, the lowest-frequency signal. “11T”and the highest-frequency signal “3T” are arranged in the test patternsignal in the order opposite to that shown in FIG. 12. In this case, thehighest-frequency signal “3T” is recorded on the first sector, that is,the B0 sector in the ECC block. The lowest-frequency signal “11T” isrecorded on the second sector, that is, the B1 sector in the ECC block.Similarly, the signal arrangement is changed between the two differentorders during later recording of the test pattern signal.

Thirty-Second Embodiment

A thirty-second embodiment of this invention is a modification of one ofthe twenty-seventh, twenty-eighth, and twenty-ninth embodiments thereof.In the thirty-second embodiment of this invention, during the firstexecution of the waveform correction optimizing process based on theevaluation method “C”, the feedback signal outputted from the monitordiode is measured while the power (the intensity) of the laser beam isset to the erasing level and is then changed to the recording level.During the second execution of the waveform correction optimizingprocess based on the evaluation method “C”, the feedback signaloutputted from the monitor diode is measured while the power (theintensity) of the laser beam is set to the recording level and is thenchanged to the erasing level. Similarly, the arrangement of the powerlevels is changed between the two different orders during the laterexecution of the waveform correction optimizing process.

Thirty-Third Embodiment

A thirty-third embodiment of this invention is a modification of one ofthe first to thirty-second embodiments thereof. In the thirty-thirdembodiment of this invention, the optical disc 22 has a predeterminedarea exclusively for storing the test pattern signal.

Thirty-Fourth Embodiment

A thirty-fourth embodiment of this invention is a modification of thethirty-third embodiment thereof. In the thirty-fourth embodiment of thisinvention, when the optical disc 22 is placed in the apparatus and thedrive of the optical disc 22 is started, the test pattern signal isrecorded on the exclusive area of the optical disc 22 and the waveformcorrection optimizing process is executed. During later recording, thewaveform correction optimizing process is executed while the testpattern signal is recorded on an area of the optical disc which isassigned to contents data.

Thirty-Fifth Embodiment

A thirty-fifth embodiment of this invention is a modification of one ofthe twenty-seventh, twenty-eighth, twenty-ninth, and thirty-secondembodiments thereof. The thirty-fifth embodiment of this inventionexecutes the waveform correction optimizing process while combining atleast two of the evaluation methods “A”, “B”, and “C” and implementingthe combined evaluation methods.

1-21. (canceled)
 22. A recording medium on which main information andmanagement information are to be recorded, wherein physicalcharacteristic information of the recording medium is to be recorded inthe management information.
 23. A recording medium as recited in claim22, comprising a lead-in area to which at least a portion of themanagement information is to be assigned, wherein the physicalcharacteristic information is to be recorded in the portion of themanagement information which is to be assigned to the lead-in area. 24.A recording medium as recited in claim 22, wherein the physicalcharacteristic information comprises physical format information of therecording medium.
 25. A recording medium as recited in claim 22, whereinthe physical characteristic information comprises recording materialinformation of the recording medium.
 26. A recording medium as recitedin claim 22, wherein the physical characteristic information comprisesoptimal recording condition information of the recording medium.
 27. Arecording medium as recited in claim 22, wherein the physicalcharacteristic information comprises linear velocity information of therecording medium.
 28. A recording medium as recited in claim 22, whereinthe physical characteristic information comprises optimal recordingcondition information and linear velocity information of the recordingmedium.
 29. A recording medium as recited in claim 22, comprising aplurality of recordable recording layers.
 30. A recording medium asrecited in claim 29, wherein the management information is to berecorded on one of the recordable recording layers.
 31. A recordingmedium as recited in claim 22, wherein the management information is tobe recorded with being of a DVD format.